input: Write a python function to merge k sorted arrays into one sorted array.
  assert mergeKArrays([[1, 3, 5], [2, 4, 6], [7, 8, 9]]) == [1, 2, 3, 4, 5, 6, 7, 8, 9]
  assert mergeKArrays([[], [2, 4, 6], [1, 5, 9]]) == [1, 2, 4, 5, 6, 9]
  assert mergeKArrays([[1], [3], [2], [4]]) == [1, 2, 3, 4]
  assert mergeKArrays([[10, 20], [15, 25], [5, 30]]) == [5, 10, 15, 20, 25, 30]
output: def mergeKArrays(arrays):
      import heapq
      min_heap = []
      result = []
  
      for array in arrays:
          for num in array:
              heapq.heappush(min_heap, num)
  
      while min_heap:
          result.append(heapq.heappop(min_heap))
  
      return result