def METHOD_NAME(vref, vcapdata):
    ifaces = [""]
    def check(dct):
        if dct.get("@qclass") == "slot" and vcapdata["slots"][dct["index"]] == vref:
            ifaces.append("(%s)" % dct.get("iface"))
        return dct
    json.loads(vcapdata["body"], object_hook=check)
    return ifaces[-1]