code: def tf_from_file(cls, path, delimiter=" "):
          
          data = np.loadtxt(path, delimiter=delimiter)
          freq = data[:, 0]
          h = data[:, 1] + 1.0j * data[:, 2]
          return np.array([freq, h]).transpose()
docs: Convert the contents of a file with the columns
          [freq, real(h), imag(h)] to a numpy.array with columns
          [freq, real(h)+j*imag(h)].
  
          Parameters
          ----------
          path : string
          delimiter : {" ", string}
  
          Return
          ------
          numpy.array