<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_token(self, act, coro, performer):

 """
 Adds a completion token `act` in the proactor with associated `coro`
 corutine and perform callable.
 """

        assert act not in self.tokens
        act.coro = coro
        self.tokens[act] = performer
        self.register_fd(act, performer)