def document(self):
        """The document representation of this read concern.

        .. note::
          :class:`ReadConcern` is immutable. Mutating the value of
          :attr:`document` does not mutate this :class:`ReadConcern`.
        """
        doc = {}
        if self.__level:
            doc['level'] = self.level
        return doc
The document representation of this read concern.

        .. note::
          :class:`ReadConcern` is immutable. Mutating the value of
          :attr:`document` does not mutate this :class:`ReadConcern`.
        
stackoverflow/venv/lib/python3.6/site-packages/pymongo/read_concern.py