Fix numpy backend

Author: fchollet

examples/demo_functional.py

@@ -5,6 +5,9 @@
 from keras_core import losses
 from keras_core import metrics
 from keras_core import optimizers
+import keras_core as keras
+
+keras.config.disable_traceback_filtering()
 
 inputs = layers.Input((100,))
 x = layers.Dense(512, activation="relu")(inputs)

keras_core/backend/exports.py

@@ -0,0 +1,20 @@
+from keras_core import backend
+from keras_core.api_export import keras_core_export
+
+if backend.backend() == "tensorflow":
+    BackendVariable = backend.tensorflow.core.Variable
+elif backend.backend() == "jax":
+    BackendVariable = backend.jax.core.Variable
+elif backend.backend() == "torch":
+    BackendVariable = backend.torch.core.Variable
+elif backend.backend() == "numpy":
+    from keras_core.backend.numpy.core import Variable as NumpyVariable
+
+    BackendVariable = NumpyVariable
+else:
+    raise RuntimeError("Invalid backend.")
+
+
+@keras_core_export("keras_core.backend.Variable")
+class Variable(BackendVariable):
+    pass

keras_core/legacy/saving/json_utils.py

@@ -184,7 +184,6 @@ def get_json_type(obj):
     #     return obj.__wrapped__
 
     if tf.available and isinstance(obj, tf.TypeSpec):
-
         from tensorflow.python.framework import type_spec_registry
 
         try: