fix: serialize head_dtype in all ImageClassifier subclasses

head_dtype was accepted by __init__() and used to set dtype policy
for classifier head layers, but was never stored on self or included
in get_config() in several ImageClassifier subclasses.

Affected models:
- VitImageClassifier
- DeiTImageClassifier
- VGGImageClassifier
- MobileNetImageClassifier
- MobileNetV5ImageClassifier
- HGNetV2ImageClassifier

This is a follow-up to keras-team#2614 which fixed the same issue in the
base ImageClassifier class.

Author: yashwanth510

keras_hub/src/models/deit/deit_image_classifier.py

@@ -115,6 +115,7 @@ def __init__(
         **kwargs,
     ):
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
 
         # === Layers ===
         self.backbone = backbone
@@ -166,6 +167,7 @@ def get_config(self):
                 "pooling": self.pooling,
                 "activation": self.activation,
                 "dropout": self.dropout,
+                "head_dtype": self.head_dtype,
             }
         )
         return config

keras_hub/src/models/hgnetv2/hgnetv2_image_classifier.py

@@ -117,6 +117,7 @@ def __init__(
     ):
         name = kwargs.get("name", "hgnetv2_image_classifier")
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
         data_format = getattr(backbone, "data_format", "channels_last")
         channel_axis = -1 if data_format == "channels_last" else 1
         self.head_filters = (
@@ -211,6 +212,7 @@ def get_config(self):
                 "activation": self.activation,
                 "dropout": self.dropout,
                 "head_filters": self.head_filters,
+                "head_dtype": self.head_dtype,
             }
         )
         return config

keras_hub/src/models/mobilenet/mobilenet_image_classifier.py

@@ -24,6 +24,7 @@ def __init__(
         **kwargs,
     ):
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
         data_format = getattr(backbone, "data_format", None)
 
         # === Layers ===
@@ -79,6 +80,7 @@ def get_config(self):
             {
                 "num_classes": self.num_classes,
                 "num_features": self.num_features,
+                "head_dtype": self.head_dtype,
             }
         )
         return config

keras_hub/src/models/mobilenetv5/mobilenetv5_image_classifier.py

@@ -88,6 +88,7 @@ def __init__(
         **kwargs,
     ):
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
         data_format = getattr(backbone, "data_format", "channels_last")
 
         # === Layers ===
@@ -152,6 +153,7 @@ def get_config(self):
                 "head_hidden_size": self.head_hidden_size,
                 "global_pool": self.global_pool_type,
                 "drop_rate": self.drop_rate,
+                "head_dtype": self.head_dtype,
             }
         )
         return config

keras_hub/src/models/vgg/vgg_image_classifier.py

@@ -114,6 +114,7 @@ def __init__(
         **kwargs,
     ):
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
         data_format = getattr(backbone, "data_format", None)
 
         # === Layers ===
@@ -211,6 +212,7 @@ def get_config(self):
                 "activation": self.activation,
                 "pooling_hidden_dim": self.pooling_hidden_dim,
                 "dropout": self.dropout,
+                "head_dtype": self.head_dtype,
             }
         )
         return config

keras_hub/src/models/vit/vit_image_classifier.py

@@ -120,6 +120,7 @@ def __init__(
         **kwargs,
     ):
         head_dtype = head_dtype or backbone.dtype_policy
+        self.head_dtype = head_dtype
 
         # === Layers ===
         self.backbone = backbone
@@ -182,6 +183,7 @@ def get_config(self):
                 "intermediate_dim": self.intermediate_dim,
                 "activation": self.activation,
                 "dropout": self.dropout,
+                "head_dtype": self.head_dtype,
             }
         )
         return config