'Add the specified users or groups to this project role. One of ``users`` or ``groups`` must be specified.
:param users: a user or users to add to the role
:type users: string, list or tuple
:param groups: a group or groups to add to the role
:type groups: string, list or tuple'

def update(self, users=None, groups=None):

    if ((users is not None) and isinstance(users, string_types)):
        users = (users,)
    if ((groups is not None) and isinstance(groups, string_types)):
        groups = (groups,)
    data = {u'id': self.id, u'categorisedActors': {u'atlassian-user-role-actor': users, u'atlassian-group-role-actor': groups}}
    super(Role, self).update(**data)
