def delete_project_actors(self, project_key, role_id, actor, actor_type=None):
        """
        Deletes actors (users or groups) from a project role.
        Delete a user from the role: /rest/api/2/project/{projectIdOrKey}/role/{roleId}?user={username}
        Delete a group from the role: /rest/api/2/project/{projectIdOrKey}/role/{roleId}?group={groupname}
        :param project_key:
        :param role_id:
        :param actor:
        :param actor_type: str : group or user string
        :return:
        """
        url = 'rest/api/2/project/{projectIdOrKey}/role/{roleId}'.format(projectIdOrKey=project_key,
                                                                         roleId=role_id)
        params = {}
        if actor_type is not None and actor_type in ['group', 'user']:
            params[actor_type] = actor
        return self.delete(url, params=params)