docs: def read_wv_master_file(wv_master_file, lines='brightest', debugplot=0):
      """read arc line wavelengths from external file.
  
      Parameters
      ----------
      wv_master_file : string
          File name of txt file containing the wavelength database.
      lines : string
          Indicates which lines to read. For files with a single column
          or two columns this parameter is irrelevant. For files with
          three columns, lines='brightest' indicates that only the
          brightest lines are read, whereas lines='all' means that all
          the lines are considered.
      debugplot : int
          Determines whether intermediate computations and/or plots
          are displayed. The valid codes are defined in
          numina.array.display.pause_debugplot.
  
      Returns
      -------
      wv_master : 1d numpy array
          Array with arc line wavelengths.
  
      """
  
      # protection
      if lines not in ['brightest', 'all']:
          raise ValueError('Unexpected lines=' + str(lines))
  
      # read table from txt file
      master_table = np.genfromtxt(wv_master_file)
  
      wv_master = read_wv_master_from_array(master_table, lines)
  
      if abs(debugplot) >= 10:
          print("Reading master table: " + wv_master_file)
          print("wv_master:\n", wv_master)
  
      return wv_master