code: def fire(self, sender=None, **params):
          '''Fire callbacks from a ``sender``.'''
          keys = (_make_id(None), _make_id(sender))
          results = []
          for (_, key), callback in self.callbacks:
              if key in keys:
                  results.append(callback(self, sender, **params))
          return resultf fire(self, sender=None, **params):
          '''Fire callbacks from a ``sender``.'''
          keys = (_make_id(None), _make_id(sender))
          results = []
          for (_, key), callback in self.callbacks:
              if key in keys:
                  results.append(callback(self, sender, **params))
          return results
docs: Fire callbacks from a ``sender``.