code: def validate_document_class(option, value):
      
      if not issubclass(value, (collections.MutableMapping, RawBSONDocument)):
          raise TypeError("%s must be dict, bson.son.SON, "
                          "bson.raw_bson.RawBSONDocument, or a "
                          "sublass of collections.MutableMapping" % (option,))
      return value
docs: Validate the document_class option.