Loosen class requirements in from_preset

* Push all the preset loading logic to the preset loader class.
* Loosen restrictions on what tokenizers/image converts can be loaded with what
  backbones.
* Fix some bugs with converters.
* Pass user kwargs around explicitly as dicts instead of using **kwargs
  everywhere (which is less safe).

Author: mattdangerw

keras_hub/src/layers/preprocessing/audio_converter.py

@@ -3,7 +3,6 @@
     PreprocessingLayer,
 )
 from keras_hub.src.utils.preset_utils import builtin_presets
-from keras_hub.src.utils.preset_utils import find_subclass
 from keras_hub.src.utils.preset_utils import get_preset_loader
 from keras_hub.src.utils.preset_utils import get_preset_saver
 from keras_hub.src.utils.python_utils import classproperty
@@ -89,10 +88,7 @@ class like `keras_hub.models.AudioConverter.from_preset()`, or from a
         ```
         """
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        if cls.backbone_cls != backbone_cls:
-            cls = find_subclass(preset, cls, backbone_cls)
-        return loader.load_audio_converter(cls, **kwargs)
+        return loader.load_audio_converter(cls=cls, kwargs=kwargs)
 
     def save_to_preset(self, preset_dir):
         """Save audio converter to a preset directory.

keras_hub/src/layers/preprocessing/image_converter.py

@@ -11,7 +11,6 @@
 )
 from keras_hub.src.utils.keras_utils import standardize_data_format
 from keras_hub.src.utils.preset_utils import builtin_presets
-from keras_hub.src.utils.preset_utils import find_subclass
 from keras_hub.src.utils.preset_utils import get_preset_loader
 from keras_hub.src.utils.preset_utils import get_preset_saver
 from keras_hub.src.utils.python_utils import classproperty
@@ -380,10 +379,7 @@ def from_preset(
         ```
         """
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        if cls.backbone_cls != backbone_cls:
-            cls = find_subclass(preset, cls, backbone_cls)
-        return loader.load_image_converter(cls, **kwargs)
+        return loader.load_image_converter(cls=cls, kwargs=kwargs)
 
     def save_to_preset(self, preset_dir):
         """Save image converter to a preset directory.

keras_hub/src/models/backbone.py

@@ -168,14 +168,9 @@ class like `keras_hub.models.Backbone.from_preset()`, or from
         ```
         """
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        if not issubclass(backbone_cls, cls):
-            raise ValueError(
-                f"Saved preset has type `{backbone_cls.__name__}` which is not "
-                f"a subclass of calling class `{cls.__name__}`. Call "
-                f"`from_preset` directly on `{backbone_cls.__name__}` instead."
-            )
-        return loader.load_backbone(backbone_cls, load_weights, **kwargs)
+        return loader.load_backbone(
+            cls=cls, load_weights=load_weights, kwargs=kwargs
+        )
 
     def save_to_preset(self, preset_dir, max_shard_size=10):
         """Save backbone to a preset directory.

keras_hub/src/models/preprocessor.py

@@ -6,7 +6,6 @@
 )
 from keras_hub.src.utils.preset_utils import PREPROCESSOR_CONFIG_FILE
 from keras_hub.src.utils.preset_utils import builtin_presets
-from keras_hub.src.utils.preset_utils import find_subclass
 from keras_hub.src.utils.preset_utils import get_preset_loader
 from keras_hub.src.utils.preset_utils import get_preset_saver
 from keras_hub.src.utils.python_utils import classproperty
@@ -171,43 +170,38 @@ def from_preset(
         )
         ```
         """
-        if cls == Preprocessor:
+        if cls is Preprocessor:
             raise ValueError(
                 "Do not call `Preprocessor.from_preset()` directly. Instead "
                 "choose a particular task preprocessing class, e.g. "
                 "`keras_hub.models.TextClassifierPreprocessor.from_preset()`."
             )
 
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        # Detect the correct subclass if we need to.
-        if cls.backbone_cls != backbone_cls:
-            cls = find_subclass(preset, cls, backbone_cls)
-        return loader.load_preprocessor(cls, config_file, **kwargs)
+        return loader.load_preprocessor(
+            cls=cls, config_file=config_file, kwargs=kwargs
+        )
 
     @classmethod
-    def _add_missing_kwargs(cls, loader, kwargs):
-        """Fill in required kwargs when loading from preset.
-
-        This is a private method hit when loading a preprocessing layer that
-        was not directly saved in the preset. This method should fill in
-        all required kwargs required to call the class constructor. For almost,
-        all preprocessors, the only required args are `tokenizer`,
-        `image_converter`, and `audio_converter`, but this can be overridden,
-        e.g. for a preprocessor with multiple tokenizers for different
-        encoders.
+    def _from_defaults(cls, loader, kwargs):
+        """Load a preprocessor from default values.
+
+        This is a private method hit for loading a preprocessing layer that was
+        not directly saved in the preset. Usually this means loading a
+        tokenizer, image_converter and/or audio_converter and calling the
+        constructor. But this can be overridden by subclasses as needed.
         """
+        defaults = {}
+        # Allow loading any tokenizer, image_converter or audio_converter config
+        # we find on disk. We allow mixing a matching tokenizers and
+        # preprocessing layers (though this is usually not a good idea).
         if "tokenizer" not in kwargs and cls.tokenizer_cls:
-            kwargs["tokenizer"] = loader.load_tokenizer(cls.tokenizer_cls)
+            defaults["tokenizer"] = loader.load_tokenizer()
         if "audio_converter" not in kwargs and cls.audio_converter_cls:
-            kwargs["audio_converter"] = loader.load_audio_converter(
-                cls.audio_converter_cls
-            )
+            defaults["audio_converter"] = loader.load_audio_converter()
         if "image_converter" not in kwargs and cls.image_converter_cls:
-            kwargs["image_converter"] = loader.load_image_converter(
-                cls.image_converter_cls
-            )
-        return kwargs
+            defaults["image_converter"] = loader.load_image_converter()
+        return cls(**{**defaults, **kwargs})
 
     def load_preset_assets(self, preset):
         """Load all static assets needed by the preprocessing layer.

keras_hub/src/models/task.py

@@ -6,13 +6,11 @@
 from keras_hub.src.api_export import keras_hub_export
 from keras_hub.src.layers.preprocessing.audio_converter import AudioConverter
 from keras_hub.src.layers.preprocessing.image_converter import ImageConverter
-from keras_hub.src.models.backbone import Backbone
 from keras_hub.src.models.preprocessor import Preprocessor
 from keras_hub.src.tokenizers.tokenizer import Tokenizer
 from keras_hub.src.utils.keras_utils import print_msg
 from keras_hub.src.utils.pipeline_model import PipelineModel
 from keras_hub.src.utils.preset_utils import builtin_presets
-from keras_hub.src.utils.preset_utils import find_subclass
 from keras_hub.src.utils.preset_utils import get_preset_loader
 from keras_hub.src.utils.preset_utils import get_preset_saver
 from keras_hub.src.utils.python_utils import classproperty
@@ -175,27 +173,38 @@ def from_preset(
         )
         ```
         """
-        if cls == Task:
+        if cls is Task:
             raise ValueError(
                 "Do not call `Task.from_preset()` directly. Instead call a "
                 "particular task class, e.g. "
                 "`keras_hub.models.TextClassifier.from_preset()`."
             )
 
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        # Detect the correct subclass if we need to.
-        if (
-            issubclass(backbone_cls, Backbone)
-            and cls.backbone_cls != backbone_cls
-        ):
-            cls = find_subclass(preset, cls, backbone_cls)
-        # Specifically for classifiers, we never load task weights if
-        # num_classes is supplied. We handle this in the task base class because
-        # it is the same logic for classifiers regardless of modality (text,
-        # images, audio).
-        load_task_weights = "num_classes" not in kwargs
-        return loader.load_task(cls, load_weights, load_task_weights, **kwargs)
+        return loader.load_task(
+            cls=cls, load_weights=load_weights, kwargs=kwargs
+        )
+
+    @classmethod
+    def _from_defaults(cls, loader, load_weights, kwargs, backbone_kwargs):
+        """Load a task from default values.
+
+        This is a private method hit for loading a task layer that was
+        not directly saved in the preset. Usually this means loading a backbone
+        and preprocessor and calling the constructor. But this can be overridden
+        by subclasses as needed.
+        """
+        defaults = {}
+        if "backbone" not in kwargs:
+            defaults["backbone"] = loader.load_backbone(
+                load_weights=load_weights, kwargs=backbone_kwargs
+            )
+        if "preprocessor" not in kwargs and cls.preprocessor_cls:
+            # Only load the "matching" preprocessor class for a task class.
+            defaults["preprocessor"] = loader.load_preprocessor(
+                cls=cls.preprocessor_cls
+            )
+        return cls(**{**defaults, **kwargs})
 
     def load_task_weights(self, filepath):
         """Load only the tasks specific weights not in the backbone."""

keras_hub/src/tokenizers/tokenizer.py

@@ -7,7 +7,6 @@
 from keras_hub.src.utils.preset_utils import ASSET_DIR
 from keras_hub.src.utils.preset_utils import TOKENIZER_CONFIG_FILE
 from keras_hub.src.utils.preset_utils import builtin_presets
-from keras_hub.src.utils.preset_utils import find_subclass
 from keras_hub.src.utils.preset_utils import get_file
 from keras_hub.src.utils.preset_utils import get_preset_loader
 from keras_hub.src.utils.preset_utils import get_preset_saver
@@ -257,7 +256,6 @@ class like `keras_hub.models.Tokenizer.from_preset()`, or from
         ```
         """
         loader = get_preset_loader(preset)
-        backbone_cls = loader.check_backbone_class()
-        if cls.backbone_cls != backbone_cls:
-            cls = find_subclass(preset, cls, backbone_cls)
-        return loader.load_tokenizer(cls, config_file, **kwargs)
+        return loader.load_tokenizer(
+            cls=cls, config_file=config_file, kwargs=kwargs
+        )