<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def new_signal(celf, path, iface, name) :
        "creates a new DBUS.MESSAGE_TYPE_SIGNAL message."
        result = dbus.dbus_message_new_signal(path.encode(), iface.encode(), name.encode())
        if result == None :
            raise CallFailed("dbus_message_new_signal")
        #end if
        return \
            celf(result)