code: def test_heapify(self):
      h = [5, 4, 3, 2, 1, 0]
      q = self._make_mapped_queue(h)
      q._heapify()
      self._check_map(q)
  
imports: import pytest
  from networkx.utils.mapped_queue import MappedQueue, _HeapElement
label_desc: Use image node_id 4 for calling the TestMappedQueue obj's underlying member method code with example usage: obj.test_heapify() without return types