      "                return None\n",
      "            if slow.data == fast.data:\n",
      "                break\n",
      "        slow = self.head\n",
      "        while slow.data != fast.data:\n",
      "            slow = slow.next\n",
      "            fast = fast.next\n",
      "            if fast is None:\n",
      "                return None\n",
      "        return slow.data"
 
</s> remove     "            if slow.data == fast.data:\n",
 </s> add     "            if slow == fast:\n", </s> remove    "version": "3.4.3"
 </s> add    "version": "3.5.0" </s> remove    "pygments_lexer": "ipython2",
   "version": "2.7.10"
 </s> add    "pygments_lexer": "ipython3",
   "version": "3.5.0" </s> remove     "version": 2
 </s> add     "version": 3 </s> remove    "name": "python2"
 </s> add    "name": "python3"
    "        while slow != fast:\n",
      "                return None\n",
      "            if slow.data == fast.data:\n",
      "                break\n",
      "        slow = self.head\n",
    "        while slow != fast:\n",
      "            slow = slow.next\n",
      "            fast = fast.next\n",
      "            if fast is None:\n",
      "                return None\n",
      "        return slow.data"
keep keep keep keep replace keep keep keep keep keep
 Polish find loop start challenge and solution

Change slow and fast nodes equality check from their data value to an object check. 
linked_lists/find_loop_start/find_loop_start_solution.ipynb