def _get_database(self, database_name):
        """
        Get PyMongo client pointing to the current database.

        :return: MongoDB client of the current database.
        :raise DataSourceError
        """
        try:
            return self._client[database_name]
        except InvalidName as ex:
            raise DataSourceError("Cannot connect to database %s!"
                                  % self._database) from ex
Get PyMongo client pointing to the current database.

        :return: MongoDB client of the current database.
        :raise DataSourceError