def foreign_keys(self):
        """https://github.com/frictionlessdata/tableschema-py#schema
        """
        foreign_keys = self.__current_descriptor.get('foreignKeys', [])
        for key in foreign_keys:
            key.setdefault('fields', [])
            key.setdefault('reference', {})
            key['reference'].setdefault('resource', '')
            key['reference'].setdefault('fields', [])
            if not isinstance(key['fields'], list):
                key['fields'] = [key['fields']]
            if not isinstance(key['reference']['fields'], list):
                key['reference']['fields'] = [key['reference']['fields']]
        return foreign_keys
https://github.com/frictionlessdata/tableschema-py#schema