code: def linear(x):
      """Linear activation function (pass-through).
  
      A "linear" activation is an identity function:
      it returns the input, unmodified.
  
      Args:
          x: Input tensor.
      """
      return x
  
imports: from keras import backend
  from keras import ops
  from keras.api_export import keras_export
label_desc: Use image node_id 16 for calling a global function with example usage: linear(x) and returns: x