docs: def _merge_data(self, data: AnyMapping, *additional: AnyMapping) -> dict:
          r"""Merge base data and additional dicts.
  
          :param data: Base data.
          :param \*additional: Additional data dicts to be merged into base dict.
          """
          return defaults(
              dict(data) if not isinstance(data, dict) else data,
              *(dict(item) for item in additional))