docs: def add_history(self, line):
          u'''Append a line to the history buffer, as if it was the last line typed.'''
          if not hasattr(line, "get_line_text"):
              line = lineobj.ReadLineTextBuffer(line)
          if not line.get_line_text():
              pass
          elif len(self.history) > 0 and self.history[-1].get_line_text() == line.get_line_text():
              pass
          else:
              self.history.append(line)
          self.history_cursor = len(self.history)