      "        sorted_data = merge_sort(data)\n",
      "        assert_equal(sorted_data, None)\n",
      "\n",
      "        print('Empty input')\n",
      "        data = []\n",
      "        sorted_data = merge_sort(data)\n",
      "        assert_equal(sorted_data, [])\n",
      "\n",
      "        print('One element')\n",
      "        data = [5]\n",
      "        sorted_data = merge_sort(data)\n",
      "        assert_equal(sorted_data, [5])\n",
 
</s>
    "        assert_equal(merge_sort.sort([]), [])\n",
      "        sorted_data = merge_sort(data)\n",
      "        assert_equal(sorted_data, None)\n",
      "\n",
      "        print('Empty input')\n",
    "        assert_equal(merge_sort.sort([]), [])\n",
    "        assert_equal(merge_sort.sort([]), [])\n",
    "        assert_equal(merge_sort.sort([]), [])\n",
      "\n",
      "        print('One element')\n",
      "        data = [5]\n",
      "        sorted_data = merge_sort(data)\n",
      "        assert_equal(sorted_data, [5])\n",
keep keep keep keep replace replace replace keep keep keep keep keep
 Update merge sort challenge (#130)

Update constraints, test cases, code, and tests.
sorting_searching/merge_sort/merge_sort_solution.ipynb