code: def check_num_columns_in_param_list_arrays(param_list):
      
      try:
          num_columns = param_list[0].shape[1]
          assert all([x is None or (x.shape[1] == num_columns)
                      for x in param_list])
      except AssertionError:
          msg = "param_list arrays should have equal number of columns."
          raise ValueError(msg)
  
      return None
docs: Ensure that each array in param_list, that is not None, has the same number
      of columns. Raises a helpful ValueError if otherwise.
  
      Parameters
      ----------
      param_list : list of ndarrays or None.
  
      Returns
      -------
      None.