Added TF TransfoXL Sequence Classification (#9169)

* TF Transfoxl seq classification

* Update test_modeling_tf_transfo_xl.py

Added num_labels to config level

* TF Transfoxl seq classification

* Update test_modeling_tf_transfo_xl.py

Added num_labels to config level

* code refactor

* code refactor

* code refator

src/transformers/__init__.py

@@ -899,6 +899,7 @@ if is_tf_available():
     from .models.transfo_xl import (
         TF_TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST,
         TFAdaptiveEmbedding,
+        TFTransfoXLForSequenceClassification,
         TFTransfoXLLMHeadModel,
         TFTransfoXLMainLayer,
         TFTransfoXLModel,

src/transformers/models/auto/modeling_tf_auto.py

@@ -131,7 +131,11 @@ from ..roberta.modeling_tf_roberta import (
     TFRobertaModel,
 )
 from ..t5.modeling_tf_t5 import TFT5ForConditionalGeneration, TFT5Model
-from ..transfo_xl.modeling_tf_transfo_xl import TFTransfoXLLMHeadModel, TFTransfoXLModel
+from ..transfo_xl.modeling_tf_transfo_xl import (
+    TFTransfoXLForSequenceClassification,
+    TFTransfoXLLMHeadModel,
+    TFTransfoXLModel,
+)
 from ..xlm.modeling_tf_xlm import (
     TFXLMForMultipleChoice,
     TFXLMForQuestionAnsweringSimple,
@@ -342,6 +346,7 @@ TF_MODEL_FOR_SEQUENCE_CLASSIFICATION_MAPPING = OrderedDict(
         (GPT2Config, TFGPT2ForSequenceClassification),
         (MPNetConfig, TFMPNetForSequenceClassification),
         (OpenAIGPTConfig, TFOpenAIGPTForSequenceClassification),
+        (TransfoXLConfig, TFTransfoXLForSequenceClassification),
         (CTRLConfig, TFCTRLForSequenceClassification),
     ]
 )

src/transformers/models/transfo_xl/__init__.py

@@ -36,6 +36,7 @@ if is_tf_available():
     from .modeling_tf_transfo_xl import (
         TF_TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST,
         TFAdaptiveEmbedding,
+        TFTransfoXLForSequenceClassification,
         TFTransfoXLLMHeadModel,
         TFTransfoXLMainLayer,
         TFTransfoXLModel,

src/transformers/models/transfo_xl/modeling_tf_transfo_xl.py

@@ -28,7 +28,14 @@ from ...file_utils import (
     add_start_docstrings,
     add_start_docstrings_to_model_forward,
 )
-from ...modeling_tf_utils import TFPreTrainedModel, get_initializer, input_processing, keras_serializable, shape_list
+from ...modeling_tf_utils import (
+    TFPreTrainedModel,
+    TFSequenceClassificationLoss,
+    get_initializer,
+    input_processing,
+    keras_serializable,
+    shape_list,
+)
 from ...utils import logging
 from .configuration_transfo_xl import TransfoXLConfig
 from .modeling_tf_transfo_xl_utilities import TFAdaptiveSoftmaxMask
@@ -717,6 +724,40 @@ class TFTransfoXLLMHeadModelOutput(ModelOutput):
     attentions: Optional[Tuple[tf.Tensor]] = None
 
 
+@dataclass
+class TFTransfoXLSequenceClassifierOutputWithPast(ModelOutput):
+    """
+    Base class for outputs of sentence classification models.
+
+    Args:
+        loss (:obj:`tf.Tensor` of shape :obj:`(1,)`, `optional`, returned when :obj:`labels` is provided):
+            Classification (or regression if config.num_labels==1) loss.
+        logits (:obj:`tf.Tensor` of shape :obj:`(batch_size, config.num_labels)`):
+            Classification (or regression if config.num_labels==1) scores (before SoftMax).
+        mems (:obj:`List[tf.Tensor]` of length :obj:`config.n_layers`):
+            Contains pre-computed hidden-states (key and values in the attention blocks). Can be used (see :obj:`mems`
+            input) to speed up sequential decoding. The token ids which have their past given to this model should not
+            be passed as input ids as they have already been computed.
+        hidden_states (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_hidden_states=True`` is passed or when ``config.output_hidden_states=True``):
+            Tuple of :obj:`tf.Tensor` (one for the output of the embeddings + one for the output of each layer) of
+            shape :obj:`(batch_size, sequence_length, hidden_size)`.
+
+            Hidden-states of the model at the output of each layer plus the initial embedding outputs.
+        attentions (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_attentions=True`` is passed or when ``config.output_attentions=True``):
+            Tuple of :obj:`tf.Tensor` (one for each layer) of shape :obj:`(batch_size, num_heads, sequence_length,
+            sequence_length)`.
+
+            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention
+            heads.
+    """
+
+    loss: Optional[tf.Tensor] = None
+    logits: tf.Tensor = None
+    mems: List[tf.Tensor] = None
+    hidden_states: Optional[Tuple[tf.Tensor]] = None
+    attentions: Optional[Tuple[tf.Tensor]] = None
+
+
 TRANSFO_XL_START_DOCSTRING = r"""
 
     This model inherits from :class:`~transformers.TFPreTrainedModel`. Check the superclass documentation for the
@@ -969,3 +1010,149 @@ class TFTransfoXLLMHeadModel(TFTransfoXLPreTrainedModel):
             inputs["mems"] = past
 
         return inputs
+
+
+@add_start_docstrings(
+    """
+    The Transfo XL Model transformer with a sequence classification head on top (linear layer).
+
+    :class:`~transformers.TFTransfoXLForSequenceClassification` uses the last token in order to do the classification,
+    as other causal models (e.g. GPT-1,GPT-2) do.
+
+    Since it does classification on the last token, it requires to know the position of the last token. If a
+    :obj:`pad_token_id` is defined in the configuration, it finds the last token that is not a padding token in each
+    row. If no :obj:`pad_token_id` is defined, it simply takes the last value in each row of the batch. Since it cannot
+    guess the padding tokens when :obj:`inputs_embeds` are passed instead of :obj:`input_ids`, it does the same (take
+    the last value in each row of the batch).
+    """,
+    TRANSFO_XL_START_DOCSTRING,
+)
+class TFTransfoXLForSequenceClassification(TFTransfoXLPreTrainedModel, TFSequenceClassificationLoss):
+    def __init__(self, config, *inputs, **kwargs):
+        super().__init__(config, *inputs, **kwargs)
+        self.num_labels = config.num_labels
+        self.score = tf.keras.layers.Dense(
+            config.num_labels,
+            kernel_initializer=get_initializer(config.init_range),
+            name="score",
+            use_bias=False,
+        )
+        self.transformer = TFTransfoXLMainLayer(config, name="transformer")
+
+    def get_output_embeddings(self):
+        return self.transformer.word_emb
+
+    @add_start_docstrings_to_model_forward(TRANSFO_XL_INPUTS_DOCSTRING)
+    @add_code_sample_docstrings(
+        tokenizer_class=_TOKENIZER_FOR_DOC,
+        checkpoint="transfo-xl-wt103",
+        output_type=TFTransfoXLSequenceClassifierOutputWithPast,
+        config_class=_CONFIG_FOR_DOC,
+    )
+    def call(
+        self,
+        input_ids=None,
+        mems=None,
+        head_mask=None,
+        inputs_embeds=None,
+        output_attentions=None,
+        output_hidden_states=None,
+        return_dict=None,
+        labels=None,
+        training=False,
+        **kwargs,
+    ):
+        r"""
+        labels (:obj:`tf.Tensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
+            Labels for computing the cross entropy classification loss. Indices should be in ``[0, ...,
+            config.vocab_size - 1]``.
+        """
+        inputs = input_processing(
+            func=self.call,
+            config=self.config,
+            input_ids=input_ids,
+            mems=mems,
+            head_mask=head_mask,
+            inputs_embeds=inputs_embeds,
+            output_attentions=output_attentions,
+            output_hidden_states=output_hidden_states,
+            return_dict=return_dict,
+            labels=labels,
+            training=training,
+            kwargs_call=kwargs,
+        )
+
+        transformer_outputs = self.transformer(
+            input_ids=inputs["input_ids"],
+            mems=inputs["mems"],
+            head_mask=inputs["head_mask"],
+            inputs_embeds=inputs["inputs_embeds"],
+            output_attentions=inputs["output_attentions"],
+            output_hidden_states=inputs["output_hidden_states"],
+            return_dict=inputs["return_dict"],
+            training=inputs["training"],
+        )
+
+        hidden_states = transformer_outputs[0]
+        logits = self.score(hidden_states)
+        logits_shape = shape_list(logits)
+        in_logits = None
+        if self.config.pad_token_id is None:
+            sequence_lengths = -1
+        else:
+            if inputs["input_ids"] is not None:
+                sequence_lengths = (
+                    tf.reduce_sum(
+                        tf.cast(tf.math.not_equal(inputs["input_ids"], self.config.pad_token_id), tf.int32),
+                        -1,
+                        keepdims=False,
+                    )
+                    - 1
+                )
+
+                def get_seq_element(sequence_position, input_batch):
+                    return tf.strided_slice(
+                        input_batch, [sequence_position, 0], [sequence_position + 1, input_batch.shape[-1]], [1, 1]
+                    )
+
+                result = tf.map_fn(
+                    fn=lambda t: get_seq_element(t[0], t[1]), elems=[sequence_lengths, logits], dtype="float"
+                )
+                in_logits = tf.reshape(result, [logits_shape[0], logits_shape[-1]])
+            else:
+                sequence_lengths = -1
+                logger.warning(
+                    f"{self.__class__.__name__} will not detect padding tokens in `inputs_embeds`. Results may be "
+                    f"unexpected if using padding tokens in conjunction with `inputs_embeds.`"
+                )
+        loss = None
+
+        if inputs["labels"] is not None:
+            if input_ids is not None:
+                batch_size, sequence_length = shape_list(inputs["input_ids"])[:2]
+            else:
+                batch_size, sequence_length = shape_list(inputs["inputs_embeds"])[:2]
+            assert (
+                self.config.pad_token_id is not None or batch_size == 1
+            ), "Cannot handle batch sizes > 1 if no padding token is defined."
+
+            if not tf.is_tensor(sequence_lengths):
+                in_logits = logits[0:batch_size, sequence_lengths]
+
+            loss = self.compute_loss(
+                tf.reshape(inputs["labels"], [-1, 1]), tf.reshape(in_logits, [-1, self.num_labels])
+            )
+
+        pooled_logits = in_logits if in_logits is not None else logits
+
+        if not inputs["return_dict"]:
+            output = (pooled_logits,) + transformer_outputs[1:]
+            return ((loss,) + output) if loss is not None else output
+
+        return TFTransfoXLSequenceClassifierOutputWithPast(
+            loss=loss,
+            logits=pooled_logits,
+            mems=transformer_outputs.mems,
+            hidden_states=transformer_outputs.hidden_states,
+            attentions=transformer_outputs.attentions,
+        )

src/transformers/utils/dummy_tf_objects.py

@@ -1302,6 +1302,15 @@ class TFAdaptiveEmbedding:
         requires_tf(self)
 
 
+class TFTransfoXLForSequenceClassification:
+    def __init__(self, *args, **kwargs):
+        requires_tf(self)
+
+    @classmethod
+    def from_pretrained(self, *args, **kwargs):
+        requires_tf(self)
+
+
 class TFTransfoXLLMHeadModel:
     def __init__(self, *args, **kwargs):
         requires_tf(self)

tests/test_modeling_tf_transfo_xl.py

@@ -27,7 +27,12 @@ from .test_modeling_tf_common import TFModelTesterMixin, ids_tensor
 if is_tf_available():
     import tensorflow as tf
 
-    from transformers import TF_TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST, TFTransfoXLLMHeadModel, TFTransfoXLModel
+    from transformers import (
+        TF_TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST,
+        TFTransfoXLForSequenceClassification,
+        TFTransfoXLLMHeadModel,
+        TFTransfoXLModel,
+    )
 
 
 class TFTransfoXLModelTester:
@@ -55,6 +60,9 @@ class TFTransfoXLModelTester:
         self.scope = None
         self.seed = 1
         self.eos_token_id = 0
+        self.num_labels = 3
+        self.pad_token_id = self.vocab_size - 1
+        self.init_range = 0.01
 
     def prepare_config_and_inputs(self):
         input_ids_1 = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
@@ -77,6 +85,9 @@ class TFTransfoXLModelTester:
             div_val=self.div_val,
             n_layer=self.num_hidden_layers,
             eos_token_id=self.eos_token_id,
+            pad_token_id=self.vocab_size - 1,
+            init_range=self.init_range,
+            num_labels=self.num_labels,
         )
 
         return (config, input_ids_1, input_ids_2, lm_labels)
@@ -131,6 +142,11 @@ class TFTransfoXLModelTester:
             [(self.mem_len, self.batch_size, self.hidden_size)] * self.num_hidden_layers,
         )
 
+    def create_and_check_transfo_xl_for_sequence_classification(self, config, input_ids_1, input_ids_2, lm_labels):
+        model = TFTransfoXLForSequenceClassification(config)
+        result = model(input_ids_1)
+        self.parent.assertEqual(result.logits.shape, (self.batch_size, self.num_labels))
+
     def prepare_config_and_inputs_for_common(self):
         config_and_inputs = self.prepare_config_and_inputs()
         (config, input_ids_1, input_ids_2, lm_labels) = config_and_inputs
@@ -141,7 +157,9 @@ class TFTransfoXLModelTester:
 @require_tf
 class TFTransfoXLModelTest(TFModelTesterMixin, unittest.TestCase):
 
-    all_model_classes = (TFTransfoXLModel, TFTransfoXLLMHeadModel) if is_tf_available() else ()
+    all_model_classes = (
+        (TFTransfoXLModel, TFTransfoXLLMHeadModel, TFTransfoXLForSequenceClassification) if is_tf_available() else ()
+    )
     all_generative_model_classes = () if is_tf_available() else ()
     # TODO: add this test when TFTransfoXLLMHead has a linear output layer implemented
     test_resize_embeddings = False
@@ -163,6 +181,10 @@ class TFTransfoXLModelTest(TFModelTesterMixin, unittest.TestCase):
         config_and_inputs = self.model_tester.prepare_config_and_inputs()
         self.model_tester.create_and_check_transfo_xl_lm_head(*config_and_inputs)
 
+    def test_transfo_xl_sequence_classification_model(self):
+        config_and_inputs = self.model_tester.prepare_config_and_inputs()
+        self.model_tester.create_and_check_transfo_xl_for_sequence_classification(*config_and_inputs)
+
     def test_model_common_attributes(self):
         config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()