<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def setup_rabbitmq(self):
 """ Setup RabbitMQ connection. Call this method after spider has set its crawler object. :return: None """


        if not self.rabbitmq_key:
            self.rabbitmq_key = '{}:start_urls'.format(self.name)

        self.server = connection.from_settings(self.crawler.settings)
        self.crawler.signals.connect(self.spider_idle, signal=signals.spider_idle)
        self.crawler.signals.connect(self.item_scraped, signal=signals.item_scraped)