def log(the_plot, message):
    """Log a message for eventual disposal by the game engine user.

  Here, "game engine user" means a user interface or an environment interface,
  for example. (Clients are not required to deal with messages, but if they do,
  this is how to get a message to them.)

  Most game implementations will not need to call this function directly---
  logging is so fundamental that the Plot object expresses a `log` method that's
  syntactic sugar for this function.

  Args:
    the_plot: the pycolab game's `Plot` object.
    message: A string message to convey to the game engine user.
  """
    the_plot.setdefault('log_messages', []).append(message)
