docs: def add_breakpoint(self, event_type, bp):
          """
          Adds a breakpoint which would trigger on `event_type`.
  
          :param event_type:  The event type to trigger on
          :param bp:          The breakpoint
          :return:            The created breakpoint.
          """
          if event_type not in event_types:
              raise ValueError("Invalid event type %s passed in. Should be one of: %s" % (event_type,
                                                                                          ", ".join(event_types))
                               )
          self._breakpoints[event_type].append(bp)