def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def _update_dimension(
        self,
        size_diff,
        total_size,
        max_visible_size,
        dimension_request_property):
    if max_visible_size is None:
      is_max_visible_size_unlimited = True
    else:
      is_max_visible_size_unlimited = max_visible_size <= 0