     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
     "pygments_lexer": "ipython3",
     "version": "3.5.0"
    }
   },
   "nbformat": 4,
   "nbformat_minor": 0
  }
 
</s> remove     "version": 3
 </s> add     "version": 2 </s> remove    "display_name": "Python 3",
 </s> add    "display_name": "Python 2", </s> remove    "name": "python3"
 </s> add    "name": "python2" </s> remove     "            self.head = None\n",
 </s> add     "            self.head = self.head.next\n",
   "pygments_lexer": "ipython2",
   "version": "2.7.12"
     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
   "pygments_lexer": "ipython2",
   "version": "2.7.12"
   "pygments_lexer": "ipython2",
   "version": "2.7.12"
    }
   },
   "nbformat": 4,
   "nbformat_minor": 0
  }
keep keep keep keep replace replace keep keep keep keep keep
 Fix #173: Bugs in linked list append and delete methods (#184) 
linked_lists/linked_list/linked_list_solution.ipynb