Return raw outputs in TextClassificationPipeline (#8328)

* Return raw outputs in TextClassificationPipeline

* Style

* Support for problem type

* Update src/transformers/pipelines/text_classification.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Apply Nicolas' comments
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

src/transformers/configuration_utils.py

@@ -288,7 +288,7 @@ class PretrainedConfig(PushToHubMixin):
         allowed_problem_types = ("regression", "single_label_classification", "multi_label_classification")
         if self.problem_type is not None and self.problem_type not in allowed_problem_types:
             raise ValueError(
-                f"The config parameter `problem_type` wasnot understood: received {self.problem_type}"
+                f"The config parameter `problem_type` was not understood: received {self.problem_type}"
                 "but only 'regression', 'single_label_classification' and 'multi_label_classification' are valid."
             )
 

src/transformers/pipelines/text_classification.py

+from typing import Optional
+
 import numpy as np
 
-from ..file_utils import add_end_docstrings, is_tf_available, is_torch_available
+from ..file_utils import ExplicitEnum, add_end_docstrings, is_tf_available, is_torch_available
 from .base import PIPELINE_INIT_ARGS, Pipeline
 
 
@@ -11,11 +13,35 @@ if is_torch_available():
     from ..models.auto.modeling_auto import MODEL_FOR_SEQUENCE_CLASSIFICATION_MAPPING
 
 
+def sigmoid(_outputs):
+    return 1.0 / (1.0 + np.exp(-_outputs))
+
+
+def softmax(_outputs):
+    maxes = np.max(_outputs, axis=-1, keepdims=True)
+    shifted_exp = np.exp(_outputs - maxes)
+    return shifted_exp / shifted_exp.sum(axis=-1, keepdims=True)
+
+
+class ClassificationFunction(ExplicitEnum):
+    SIGMOID = "sigmoid"
+    SOFTMAX = "softmax"
+    NONE = "none"
+
+
 @add_end_docstrings(
     PIPELINE_INIT_ARGS,
     r"""
         return_all_scores (:obj:`bool`, `optional`, defaults to :obj:`False`):
             Whether to return all prediction scores or just the one of the predicted class.
+        function_to_apply (:obj:`str`, `optional`, defaults to :obj:`"default"`):
+            The function to apply to the model outputs in order to retrieve the scores. Accepts four different values:
+
+            - :obj:`"default"`: if the model has a single label, will apply the sigmoid function on the output. If the
+              model has several labels, will apply the softmax function on the output.
+            - :obj:`"sigmoid"`: Applies the sigmoid function on the output.
+            - :obj:`"softmax"`: Applies the softmax function on the output.
+            - :obj:`"none"`: Does not apply any function on the output.
     """,
 )
 class TextClassificationPipeline(Pipeline):
@@ -35,7 +61,9 @@ class TextClassificationPipeline(Pipeline):
     <https://huggingface.co/models?filter=text-classification>`__.
     """
 
-    def __init__(self, return_all_scores: bool = False, **kwargs):
+    task = "text-classification"
+
+    def __init__(self, return_all_scores: bool = None, function_to_apply: str = None, **kwargs):
         super().__init__(**kwargs)
 
         self.check_model_type(
@@ -44,15 +72,45 @@ class TextClassificationPipeline(Pipeline):
             else MODEL_FOR_SEQUENCE_CLASSIFICATION_MAPPING
         )
 
-        self.return_all_scores = return_all_scores
+        if hasattr(self.model.config, "return_all_scores") and return_all_scores is None:
+            return_all_scores = self.model.config.return_all_scores
+
+        if hasattr(self.model.config, "function_to_apply") and function_to_apply is None:
+            function_to_apply = self.model.config.function_to_apply
+
+        self.return_all_scores = return_all_scores if return_all_scores is not None else False
+        self.function_to_apply = function_to_apply if function_to_apply is not None else None
 
-    def __call__(self, *args, **kwargs):
+    def __call__(
+        self,
+        *args,
+        return_all_scores: Optional[bool] = None,
+        function_to_apply: Optional[ClassificationFunction] = None,
+        **kwargs
+    ):
         """
         Classify the text(s) given as inputs.
 
         Args:
             args (:obj:`str` or :obj:`List[str]`):
                 One or several texts (or one list of prompts) to classify.
+            return_all_scores (:obj:`bool`, `optional`, defaults to :obj:`False`):
+                Whether to return scores for all labels.
+            function_to_apply (:obj:`str`, `optional`, defaults to :obj:`"default"`):
+                The function to apply to the model outputs in order to retrieve the scores. Accepts four different
+                values:
+
+                If this argument is not specified, then it will apply the following functions according to the number
+                of labels:
+
+                - If the model has a single label, will apply the sigmoid function on the output.
+                - If the model has several labels, will apply the softmax function on the output.
+
+                Possible values are:
+
+                - :obj:`"sigmoid"`: Applies the sigmoid function on the output.
+                - :obj:`"softmax"`: Applies the softmax function on the output.
+                - :obj:`"none"`: Does not apply any function on the output.
 
         Return:
             A list or a list of list of :obj:`dict`: Each result comes as list of dictionaries with the following keys:
@@ -64,11 +122,28 @@ class TextClassificationPipeline(Pipeline):
         """
         outputs = super().__call__(*args, **kwargs)
 
-        if self.model.config.num_labels == 1:
-            scores = 1.0 / (1.0 + np.exp(-outputs))
+        return_all_scores = return_all_scores if return_all_scores is not None else self.return_all_scores
+        function_to_apply = function_to_apply if function_to_apply is not None else self.function_to_apply
+
+        if function_to_apply is None:
+            if self.model.config.problem_type == "multi_label_classification" or self.model.config.num_labels == 1:
+                function_to_apply = ClassificationFunction.SIGMOID
+            elif self.model.config.problem_type == "single_label_classification" or self.model.config.num_labels > 1:
+                function_to_apply = ClassificationFunction.SOFTMAX
+
+        if isinstance(function_to_apply, str):
+            function_to_apply = ClassificationFunction[function_to_apply.upper()]
+
+        if function_to_apply == ClassificationFunction.SIGMOID:
+            scores = sigmoid(outputs)
+        elif function_to_apply == ClassificationFunction.SOFTMAX:
+            scores = softmax(outputs)
+        elif function_to_apply == ClassificationFunction.NONE:
+            scores = outputs
         else:
-            scores = np.exp(outputs) / np.exp(outputs).sum(-1, keepdims=True)
-        if self.return_all_scores:
+            raise ValueError(f"Unrecognized `function_to_apply` argument: {function_to_apply}")
+
+        if return_all_scores:
             return [
                 [{"label": self.model.config.id2label[i], "score": score.item()} for i, score in enumerate(item)]
                 for item in scores