def __init__(self, xid=None):
        """Initialize header's xid."""
        super().__init__()
        self.header.xid = randint(0, MAXID) if xid is None else xid
def __init__ ( self , xid = None ) : super ( ) . __init__ ( ) self . header . xid = randint ( 0 , MAXID ) if xid is None else xid
Initialize header's xid.