'Verify that the mind and interface supplied have the expected values
(this should really be done somewhere else, like inside a test method)
and return an avatar appropriate for the given identifier.'

def requestAvatar(self, avatarId, mind, interface):

    assert (interface == pb.IPerspective)
    assert (mind == 'BRAINS!')
    if (avatarId is checkers.ANONYMOUS):
        return (pb.IPerspective, Echoer(), (lambda : None))
    else:
        self.lastPerspective = self.perspectiveFactory(avatarId)
        self.lastPerspective.loggedIn = True
        return (pb.IPerspective, self.lastPerspective, self.lastPerspective.logout)
