Added type hints for TF: TransfoXL (#19380)

* Added type hints for TF: TransfoXL
* Added type hints for TF: TransfoXL

* Change type hints for training

* Change type hints for training

src/transformers/models/transfo_xl/modeling_tf_transfo_xl.py

@@ -542,14 +542,15 @@ class TFTransfoXLMainLayer(tf.keras.layers.Layer):
     @unpack_inputs
     def call(
         self,
-        input_ids=None,
-        mems=None,
-        head_mask=None,
-        inputs_embeds=None,
-        output_attentions=None,
-        output_hidden_states=None,
-        return_dict=None,
-        training=False,
+        input_ids: Optional[TFModelInputType] = None,
+        mems: Optional[List[tf.Tensor]] = None,
+        head_mask: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        inputs_embeds: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        output_attentions: Optional[bool] = None,
+        output_hidden_states: Optional[bool] = None,
+        return_dict: Optional[bool] = None,
+        labels: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        training: bool = False,
     ):
 
         # the original code for Transformer-XL used shapes [len, bsz] but we want a unified interface in the library
@@ -894,14 +895,14 @@ class TFTransfoXLModel(TFTransfoXLPreTrainedModel):
     )
     def call(
         self,
-        input_ids=None,
-        mems=None,
-        head_mask=None,
-        inputs_embeds=None,
-        output_attentions=None,
-        output_hidden_states=None,
-        return_dict=None,
-        training=False,
+        input_ids: Optional[TFModelInputType] = None,
+        mems: Optional[List[tf.Tensor]] = None,
+        head_mask: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        inputs_embeds: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        output_attentions: Optional[bool] = None,
+        output_hidden_states: Optional[bool] = None,
+        return_dict: Optional[bool] = None,
+        training: bool = False,
     ):
         outputs = self.transformer(
             input_ids=input_ids,
@@ -974,15 +975,15 @@ class TFTransfoXLLMHeadModel(TFTransfoXLPreTrainedModel):
     )
     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,
+        input_ids: Optional[TFModelInputType] = None,
+        mems: Optional[List[tf.Tensor]] = None,
+        head_mask: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        inputs_embeds: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        output_attentions: Optional[bool] = None,
+        output_hidden_states: Optional[bool] = None,
+        return_dict: Optional[bool] = None,
+        labels: Optional[Union[np.ndarray, tf.Tensor]] = None,
+        training: bool = False,
     ):
         if input_ids is not None:
             bsz, tgt_len = shape_list(input_ids)[:2]