Deletes a permission from a file.

        :param file_id: a spreadsheet ID (aka file ID.)
        :type file_id: str
        :param permission_id: an ID for the permission.
        :type permission_id: str

def remove_permission(self, file_id, permission_id):
        """Deletes a permission from a file.

        :param file_id: a spreadsheet ID (aka file ID.)
        :type file_id: str
        :param permission_id: an ID for the permission.
        :type permission_id: str
        """
        url = '{0}/{1}/permissions/{2}'.format(
            DRIVE_FILES_API_V2_URL,
            file_id,
            permission_id
        )

        self.request('delete', url)