     "source": [
      "## Constraints\n",
      "\n",
      "* Do we expect the return to be in reverse order too?\n",
      "    * Yes\n",
      "* What if one of the inputs is None?\n",
      "    * Return None for an invalid operation\n",
      "* How large are these numbers--can they fit in memory?\n",
      "    * Yes\n",
 
</s>
    "* Can we assume this is a non-circular, singly linked list?\n",
    "    * Yes\n",
     "source": [
      "## Constraints\n",
      "\n",
    "* Can we assume this is a non-circular, singly linked list?\n",
    "    * Yes\n",
      "* Do we expect the return to be in reverse order too?\n",
      "    * Yes\n",
      "* What if one of the inputs is None?\n",
      "    * Return None for an invalid operation\n",
      "* How large are these numbers--can they fit in memory?\n",
      "    * Yes\n",
keep keep add keep keep keep keep keep keep
 Update linked list constraints

Specify singly linked list, non circular.  Also specify the solution fits in memory.
linked_lists/add_reverse/add_reverse_challenge.ipynb