Some callers like MuTect incorporate a second caller for indels.

def _get_caller_supplement(caller, data):
    """Some callers like MuTect incorporate a second caller for indels.
    """
    if caller == "mutect":
        icaller = tz.get_in(["config", "algorithm", "indelcaller"], data)
        if icaller:
            caller = "%s/%s" % (caller, icaller)
    return caller