code: def serialize(activation):
      """Returns the string identifier of an activation function.
  
      Args:
          activation : Function object.
  
      Returns:
          String denoting the name attribute of the input function
  
      For example:
  
      >>> tf.keras.activations.serialize(tf.keras.activations.tanh)
      'tanh'
      >>> tf.keras.activations.serialize(tf.keras.activations.sigmoid)
      'sigmoid'
      >>> tf.keras.activations.serialize('abcd')
      Traceback (most recent call last):
      ...
      ValueError: ('Cannot serialize', 'abcd')
  
      Raises:
          ValueError: The input function is not a valid one.
      """
      if (
          hasattr(activation, "__name__")
          and activation.__name__ in _TF_ACTIVATIONS_V2
      ):
          return _TF_ACTIVATIONS_V2[activation.__name__]
      return serialize_keras_object(activation)
  
imports: from tensorflow.python.keras import backend
  from tensorflow.python.keras.layers import advanced_activations
  from tensorflow.python.keras.utils.generic_utils import deserialize_keras_object
  from tensorflow.python.keras.utils.generic_utils import serialize_keras_object
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn
  from tensorflow.python.util import dispatch
label_desc: Use image node_id 14 for calling a global function with example usage: serialize(activation) and returns: serialize_keras_object, _TF_ACTIVATIONS_V2