'Add a mqtt_eventstream component.'

def add_eventstream(self, sub_topic=None, pub_topic=None):

    config = {}
    if sub_topic:
        config['subscribe_topic'] = sub_topic
    if pub_topic:
        config['publish_topic'] = pub_topic
    return setup_component(self.hass, eventstream.DOMAIN, {eventstream.DOMAIN: config})
