code: def semantic(x, center=True, max_val=1.0):
      """
      Semantic adversarial examples.
  
      https://arxiv.org/abs/1703.06857
  
      Note: data must either be centered (so that the negative image can be
      made by simple negation) or must be in the interval of [-1, 1]
  
      Arguments
      ---------
      center : bool
               If true, assumes data has 0 mean so the negative image is just negation.
               If false, assumes data is in interval [0, max_val]
      max_val : float
                Maximum value allowed in the input data.
      """
  
      if center:
          return x * -1
      return max_val - x
  
label_desc: Use image node_id 1 for calling a global function with example usage: semantic(x, center, max_val) and returns: unknown, unknown