Fix this code so that it will run with proper answers, please dont use chatgpt and please test your code before submitting: import sys import heapq import copy class PriorityQueue(): def __init__(self): self.thisQueue = [] def push(self, thisNode): heapq.heappush(self.thisQueue, (thisNode.val, -thisNode.id, thisNode)) def pop(self): return heapq.heappop(self.thisQueue)[2] def isEmpty(self): return len(self.thisQueue) == 0 def length(self): return len(self.thisQueue) class Set(): def __init__(self): self.thisSet = set() def add(self, entry): if entry is not None: self.thisSet.add(entry.__hash__()) def length(self): return len(self.thisSet) def isMember(self, query): return query.__hash__() in self.thisSet class Node(): def __init__(self, val, startstate, endstate, depth): global nodeid self.id = nodeid nodeid += 1 self.val = val self.state = startstate self.endstate = endstate self.depth = depth def __str__(self): return 'Node: id=%d val=%d' % (self.id, self.val) def expand(current_node, closedlist, goal_state): closedlist.add(current_node.state) successors = [] up_child = current_node.state.up() down_child = current_node.state.down() right_child = current_node.state.right() left_child = current_node.state.left() children = [left_child, right_child, up_child, down_child] for child in children: if child is not None and not closedlist.isMember(child): s = Node(0, child, None, current_node.depth + 1) s.parent_node = current_node if child == left_child: s.action = "left" elif child == right_child: s.action = "right" elif child == up_child: s.action = "up" elif child == down_child: s.action = "down" successors.append(s) return successors def h0(currenttiles, stiles): misplaced = 0 for i in range(len(stiles)): for j in range(len(currenttiles)): if stiles[i][j] != currenttiles[i][j]: misplaced += 1 return misplaced def manhattan(currenttiles, stiles): total = 0 for i in range(len(stiles)): for j in range(len(currenttiles)): if stiles[i][j] != currenttiles[i][j]: y = stiles[i][j] a = i b = j for k in range(len(stiles)): for l in range(len(stiles)): if currenttiles[k][l] == y: d = k e = l count = (abs(d - a) + abs(e - b)) total += count return total class State(): def __init__(self): self.xpos = 0 self.ypos = 0 self.tiles = [[0, 1, 2], [3, 4, 5], [6, 7, 8]] def left(self): if self.ypos == 0: return None s = self.copy() s.tiles[s.xpos][s.ypos] = s.tiles[s.xpos][s.ypos - 1] s.ypos -= 1 s.tiles[s.xpos][s.ypos] = 0 return s def right(self): if self.ypos == 2: return None s = self.copy() s.tiles[s.xpos][s.ypos] = s.tiles[s.xpos][s.ypos + 1] s.ypos += 1 s.tiles[s.xpos][s.ypos] = 0 return s def up(self): if self.xpos == 0: return None s = self.copy() s.tiles[s.xpos][s.ypos] = s.tiles[s.xpos - 1][s.ypos] s.xpos -= 1 s.tiles[s.xpos][s.ypos] = 0 return s def down(self): if self.xpos == 2: return None s = self.copy() s.tiles[s.xpos][s.ypos] = s.tiles[s.xpos + 1][s.ypos] s.xpos += 1 s.tiles[s.xpos][s.ypos] = 0 return s def __hash__(self): return (tuple(self.tiles[.