public behaviors def init (self)"""create new empty priority queue ""self data def len (self)"""return the number of items in the priority queue ""return len(self datadef add(selfkeyvalue)"""add key-value pair to the priority queue ""self data append(self item(keyvalue)upheap newly added position self upheap(len(self data def min(self)"""return but do not remove ( ,vtuple with minimum key raise empty exception if empty ""if self is empty)raise emptypriority queue is empty item self data[ return (item keyitem valuedef remove min(self)"""remove and return ( ,vtuple with minimum key raise empty exception if empty ""if self is empty)raise emptypriority queue is empty put minimum item at the end self swap( len(self data and remove it from the listitem self data popthen fix new root self downheap( return (item keyitem valuecode fragment an implementation of priority queue using an array-based heap (continued from code fragment