      "        assert_equal(heap.extract_min(), None)\n",
      "        heap.insert(20)\n",
      "        assert_equal(heap.peek_min(), 20)\n",
      "        heap.insert(5)\n",
      "        assert_equal(heap.peek_min(), 5)\n",
      "        heap.insert(15)\n",
      "        heap.insert(22)\n",
      "        heap.insert(40)\n",
      "        heap.insert(5)\n",
      "        assert_equal(heap.peek_min(), 5)\n",
 
</s> remove     "        assert_equal(heap.peek_min(), 20)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), 20)\n", </s> remove     "        assert_equal(heap.peek_min(), 5)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), 5)\n", </s> remove     "        assert_equal(heap.peek_min(), None)\n",
    "        assert_equal(heap.extract_min(), None)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), None)\n",
    "        self.assertEqual(heap.extract_min(), None)\n", </s> remove     "        assert_equal(heap.array[0], 20)\n",
 </s> add     "        self.assertEqual(heap.array[0], 20)\n", </s> remove     "        assert_equal(heap.array[0], 5)\n",
    "        assert_equal(heap.array[1], 20)\n",
 </s> add     "        self.assertEqual(heap.array[0], 5)\n",
    "        self.assertEqual(heap.array[1], 20)\n",
    "        self.assertEqual(heap.peek_min(), 5)\n",
      "        assert_equal(heap.extract_min(), None)\n",
      "        heap.insert(20)\n",
      "        assert_equal(heap.peek_min(), 20)\n",
      "        heap.insert(5)\n",
    "        self.assertEqual(heap.peek_min(), 5)\n",
      "        heap.insert(15)\n",
      "        heap.insert(22)\n",
      "        heap.insert(40)\n",
      "        heap.insert(5)\n",
      "        assert_equal(heap.peek_min(), 5)\n",
keep keep keep keep replace keep keep keep keep keep
 #273: Remove nose dependency for graphs_trees/ (#277) 
graphs_trees/min_heap/min_heap_challenge.ipynb