Merge K sorted array

from heapq import heappush,heappop
class Solution:
    #Function to merge k sorted arrays.
    def mergeKArrays(self, arr, K):
        heap=[]
        for i in arr:
            heappush(heap,[i[0],0,i])
        ans=[]
        while len(heap)>0:
            k=heappop(heap)
            index=k[1]
            ar=k[2]
            ans.append(k[0])
            if len(ar)>index+1:
                heappush(heap,[ar[index+1],index+1,ar])
        return ans