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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_broker() -> "Broker": """Get the global broker instance. If no global broker is set, this initializes a RabbitmqBroker and returns it. Returns: Broker: The default Broker. """

    global global_broker
    if global_broker is None:
        from .brokers.rabbitmq import RabbitmqBroker

        set_broker(RabbitmqBroker(
            host="127.0.0.1",
            port=5672,
            heartbeat=5,
            connection_attempts=5,
            blocked_connection_timeout=30,
        ))
    return global_broker