code: def linear(x):
      """Linear activation function (pass-through).
  
      For example:
  
      >>> a = tf.constant([-3.0,-1.0, 0.0,1.0,3.0], dtype = tf.float32)
      >>> b = tf.keras.activations.linear(a)
      >>> b.numpy()
      array([-3., -1.,  0.,  1.,  3.], dtype=float32)
  
      Args:
          x: Input tensor.
  
      Returns:
          The input, unmodified.
      """
      return x
  
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 13 for calling a global function with example usage: linear(x) and returns: x