code: def linear(x, out=None):
      """
      Linear function.
  
      Parameters
      ----------
      x : numpy array
          Input data.
      out : numpy array, optional
          Array to hold the output data.
  
      Returns
      -------
      numpy array
          Unaltered input data.
  
      """
      if out is None or x is out:
          return x
      out[:] = x
      return out
  
file_path: madmom/madmom/ml/nn/activations.py
imports: from __future__ import absolute_import, division, print_function
  import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: linear(x, out) and returns: out, x