Added serialize function to activations.py (#23432)

ivy/functional/frontends/tensorflow/keras/activations.py

@@ -111,6 +111,44 @@ def selu(x):
     return ivy.selu(x)
 
 
+@with_supported_dtypes(
+    {"2.13.0 and below": ("float16", "float32", "float64")},
+    "tensorflow",
+)
+def serialize(activation, use_legacy_format=False):
+    # If the activation function is None, return None
+    if activation is None:
+        return None
+
+    # If the activation function is already a string, return it
+    elif isinstance(activation, str):
+        return activation
+
+    # If the activation function is callable (a function), get its name
+    elif callable(activation):
+        # Check if the function is in the custom_objects dictionary
+        if custom_objects:
+            for name, custom_func in custom_objects.items():
+                if custom_func == activation:
+                    return name
+
+        # Check if the function is in the ACTIVATION_FUNCTIONS list
+        if activation.__name__ in ACTIVATION_FUNCTIONS:
+            return activation.__name__
+
+        # Check if the function is in the TensorFlow frontend activations
+        elif activation in tf_frontend.keras.activations.__dict__.values():
+            for name, tf_func in tf_frontend.keras.activations.__dict__.items():
+                if tf_func == activation:
+                    return name
+
+        else:
+            raise ValueError(f"Unknown activation function: {activation}.")
+
+    else:
+        raise ValueError(f"Could not interpret activation function: {activation}")
+
+
 @to_ivy_arrays_and_back
 def sigmoid(x):
     return ivy.sigmoid(x)

ivy_tests/test_ivy/test_frontends/test_tensorflow/test_keras/test_activations.py

@@ -342,6 +342,50 @@ def test_tensorflow_selu(
     )
 
 
+# serialize
+@handle_frontend_test(
+    fn_tree="tensorflow.keras.activations.serialize",
+    fn_name=st.sampled_from(get_callable_functions("keras.activations")).filter(
+        lambda x: not x[0].isupper()
+        and x
+        not in [
+            "deserialize",
+            "get",
+            "keras_export",
+            "serialize",
+            "deserialize_keras_object",
+            "serialize_keras_object",
+            "get_globals",
+        ]
+    ),
+    dtype_and_data=helpers.dtype_and_values(
+        available_dtypes=helpers.get_dtypes("valid"),
+        min_value=0,
+        max_value=10,
+        shape=helpers.ints(min_value=2, max_value=5).map(lambda x: tuple([x, x])),
+    ),
+)
+def test_tensorflow_serialize(
+    *,
+    dtype_and_data,
+    fn_name,
+    fn_tree,
+    frontend,
+):
+    dtype_data, data = dtype_and_data
+    simple_test_two_function(
+        fn_name=fn_name,
+        x=data[0],
+        frontend=frontend,
+        fn_str="serialize",
+        dtype_data=dtype_data[0],
+        rtol_=1e-01,
+        atol_=1e-01,
+        ivy_submodules=["keras", "activations"],
+        framework_submodules=["keras", "activations"],
+    )
+
+
 # sigmoid
 @handle_frontend_test(
     fn_tree="tensorflow.keras.activations.sigmoid",