Usage

import smoke

class MyCls(smoke.Broker):
    appears = smoke.signal('appears')
    leaves = smoke.signal('leaves')

def say_hello(what):
    print("hello %s" % (what,))

def say_goodbye(what):
    print("good bye %s" % (what,))

# Using broker
o = MyCls()
o.subscribe("appears", say_hello)
o.publish("appears", what='world')

# Using declared signals
o = MyCls()
o.leaves.subscribe(say_goodbye)
o.leaves.publish(what='world')

# Mixing
o = MyCls()
o.subscribe("appears", say_hello)
o.appears.publish()