<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def BROKER_TYPE(self):
 """Custom setting allowing switch between rabbitmq, redis"""


        broker_type = get('BROKER_TYPE', DEFAULT_BROKER_TYPE)
        if broker_type not in SUPPORTED_BROKER_TYPES:
            log.warn("Specified BROKER_TYPE {} not supported. Backing to default {}".format(
                broker_type, DEFAULT_BROKER_TYPE))
            return DEFAULT_BROKER_TYPE
        else:
            return broker_type