<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def roll_call_handler(service, action_type, payload, props, **kwds):
 """ This action handler responds to the "roll call" emitted by the api gateway when it is brought up with the normal summary produced by the service. """

    # if the action type corresponds to a roll call
    if action_type == roll_call_type():
        # then announce the service
        await service.announce()