Merge k Sorted Lists

def mergeKLists(lists):
    head = ListNode(None)
    curr = head
    h = []
    
    for i, node in enumerate(lists):
        if node:
            heapq.heappush(h, (node.val, i, node))
            
    while h:
        val, i, node = heapq.heappop(h)
        curr.next = node
        curr = node
        if node.next:
            heapq.heappush(h, (node.next.val, i, node.next))
            
    return head.next