code: def _history_move(self, p_step):
          
          if len(self.history) > 0:
              # don't pollute real history - use temporary storage
              self.history_tmp[self.history_pos] = self.edit_text
              self.history_pos = self.history_pos + p_step
              self.set_edit_text(self.history_tmp[self.history_pos])
docs: Changes current value of the command-line to the value obtained from
          history_tmp list with index calculated by addition of p_step to the
          current position in the command history (history_pos attribute).
  
          Also saves value of the command-line (before changing it) to history_tmp
          for potential later access.