Stop storing references to bound methods via tf.function (#24146)

* Stop storing references to bound methods in tf.functions

* Remove the gc.collect calls now that we resolved the underlying problem

* Remove the default signature from model.serving entirely, big cleanup

* Remove _prune_signature as self.input_signature can prune itself

* Restore serving docstring

* Update int support test to check the input signature

* Make sure other tests also use model.input_signature and not serving.input_signature

* Restore _prune_signature

* Remove the doctest GC now it's no longer needed

* Correct core tests to use the pruned sig

* order lines correctly in core tests

* Add eager_serving back with a deprecation warning

tests/utils/test_modeling_tf_core.py

@@ -217,17 +217,18 @@ class TFCoreModelTesterMixin:
         for model_class in self.all_model_classes:
             class_inputs_dict = self._prepare_for_class(inputs_dict, model_class)
             model = model_class(config)
+            class_sig = model._prune_signature(model.input_signature)
             num_out = len(model(class_inputs_dict))
 
             for key in list(class_inputs_dict.keys()):
                 # Remove keys not in the serving signature, as the SavedModel will not be compiled to deal with them
-                if key not in model.serving.input_signature[0]:
+                if key not in class_sig:
                     del class_inputs_dict[key]
                 # Check it's a tensor, in case the inputs dict has some bools in it too
                 elif isinstance(class_inputs_dict[key], tf.Tensor) and class_inputs_dict[key].dtype.is_integer:
                     class_inputs_dict[key] = tf.cast(class_inputs_dict[key], tf.int32)
 
-            if set(class_inputs_dict.keys()) != set(model.serving.input_signature[0].keys()):
+            if set(class_inputs_dict.keys()) != set(class_sig.keys()):
                 continue  # Some models have inputs that the preparation functions don't create, we skip those
 
             with tempfile.TemporaryDirectory() as tmpdirname: