code: def assign(self, role):
          '''Assign :class:`Role` ``role`` to this :class:`Subject`. If this
  :class:`Subject` is the :attr:`Role.owner`, this method does nothing.'''
          if role.owner_id != self.id:
              return self.roles.add(rolef assign(self, role):
          '''Assign :class:`Role` ``role`` to this :class:`Subject`. If this
  :class:`Subject` is the :attr:`Role.owner`, this method does nothing.'''
          if role.owner_id != self.id:
              return self.roles.add(role)
docs: Assign :class:`Role` ``role`` to this :class:`Subject`. If this
  :class:`Subject` is the :attr:`Role.owner`, this method does nothing.