docs: def set_all_file_column_labels(self, xlabel=None, ylabel=None):
          """Indicate general x,y column labels.
  
          This sets the general x and y column labels into data files for all plots.
          It can be overridden for specific plots.
  
          Args:
              xlabel/ylabel (str, optional): String indicating column label for x,y values
                  into the data files. Default is None.
  
          Raises:
              UserWarning: If xlabel and ylabel are both not specified,
                  The user will be alerted, but the code will not stop.
  
          """
          if xlabel is not None:
              self.general.x_column_label = xlabel
          if ylabel is not None:
              self.general.y_column_label = ylabel
          if xlabel is None and ylabel is None:
              warnings.warn("is not specifying x or y lables even"
                            + "though column labels function is called.", UserWarning)
          return