def METHOD_NAME(self):
    """
    A prompt-toolkit function to define the bottom toolbar.
    Described at http://python-prompt-toolkit.readthedocs.io/en/latest/pages/building_prompts.html#adding-a-bottom-toolbar
    """
    my_history = [self.symbols[action] for action in self.history]
    opponent_history = [
        self.symbols[action] for action in self.history.coplays
    ]
    history = list(zip(my_history, opponent_history))
    if self.history:
        content = "History ({}, opponent): {}".format(
            self.human_name, history
        )
    else:
        content = ""
    return content