code: def laplacian(var, dh2):
      """(1D array, dx^2) -> laplacian(1D array)
      periodic_laplacian_1D_4th_order
      Implementing the 4th order 1D laplacian with periodic condition
      """
      lap = numpy.zeros_like(var)
      lap[1:] = (4.0 / 3.0) * var[:-1]
      lap[0] = (4.0 / 3.0) * var[1]
      lap[:-1] += (4.0 / 3.0) * var[1:]
      lap[-1] += (4.0 / 3.0) * var[0]
      lap += (-5.0 / 2.0) * var
  
      lap[2:] += (-1.0 / 12.0) * var[:-2]
      lap[:2] += (-1.0 / 12.0) * var[-2:]
      lap[:-2] += (-1.0 / 12.0) * var[2:]
      lap[-2:] += (-1.0 / 12.0) * var[:2]
  
      return lap / dh2
  
label_desc: Use image node_id 1 for calling a global function with example usage: laplacian(var, dh2) and returns: unknown