docs: def _get_master_schema(version):
      # type: (Hashable) -> bytes
      """ Loads the master schema of given version as bytes.
  
          :param version: The version of the master schema whose path we
              wish to retrieve.
          :raises SchemaError: When the schema version is unknown. This
              usually means that either (a) clkhash is out of date, or (b)
              the schema version listed is incorrect.
          :return: Bytes of the schema.
      """
      try:
          file_name = MASTER_SCHEMA_FILE_NAMES[version]
      except (TypeError, KeyError) as e:
          msg = ('Schema version {} is not supported. '
                 'Consider updating clkhash.').format(version)
          raise_from(SchemaError(msg), e)
  
      try:
          schema_bytes = pkgutil.get_data('clkhash', 'schemas/{}'.format(file_name))
      except IOError as e:  # In Python 3 we can be more specific with
          # FileNotFoundError, but that doesn't exist in
          # Python 2.
          msg = ('The master schema could not be found. The schema cannot be '
                 'validated. Please file a bug report.')
          raise_from(MasterSchemaError(msg), e)
  
      if schema_bytes is None:
          msg = ('The master schema could not be loaded. The schema cannot be '
                 'validated. Please file a bug report.')
          raise MasterSchemaError(msg)
  
      return schema_bytes