      "        linked_list = LinkedList(None)\n",
      "        linked_list.insert_to_front(10)\n",
      "        assert_equal(linked_list.get_all_data(), [10])\n",
      "\n",
      "        print('Test: insert_to_front on a NULL')\n",
      "        linked_list.insert_to_front(None)\n",
      "        assert_equal(linked_list.get_all_data(), [10])\n",
      "\n",
      "        print('Test: insert_to_front general case')\n",
      "        linked_list.insert_to_front('a')\n",
 
</s> remove     "        print('Test: insert_to_front on a NULL')\n",
 </s> add     "        print('Test: insert_to_front on a None')\n", </s> remove     "        print('Test: append a NULL')\n",
 </s> add     "        print('Test: append a None')\n", </s> remove     "        print('Test: append a NULL')\n",
 </s> add     "        print('Test: append a None')\n", </s> remove     "        print('Test: delete a NULL')\n",
 </s> add     "        print('Test: delete a None')\n", </s> remove     "        print('Test: delete a NULL')\n",
 </s> add     "        print('Test: delete a None')\n",
    "        print('Test: insert_to_front on a None')\n",
      "        linked_list = LinkedList(None)\n",
      "        linked_list.insert_to_front(10)\n",
      "        assert_equal(linked_list.get_all_data(), [10])\n",
      "\n",
    "        print('Test: insert_to_front on a None')\n",
      "        linked_list.insert_to_front(None)\n",
      "        assert_equal(linked_list.get_all_data(), [10])\n",
      "\n",
      "        print('Test: insert_to_front general case')\n",
      "        linked_list.insert_to_front('a')\n",
keep keep keep keep replace keep keep keep keep keep
 Changed discussions of NULL to None to be more Pythonic. 
linked_lists/linked_list/linked_list_challenge.ipynb