     "source": [
      "## Test Cases\n",
      "\n",
      "* Empty input -> []\n",
      "* One element -> [element]\n",
      "* Two or more elements"
     ]
 
</s> remove     "    if len(data) < 2:\n",
 </s> add     "    if data is None or len(data) < 2:\n",
    "* None -> None\n",
     "source": [
      "## Test Cases\n",
      "\n",
    "* None -> None\n",
      "* Empty input -> []\n",
      "* One element -> [element]\n",
      "* Two or more elements"
     ]
keep keep add keep keep keep keep
 Add None input test case to insertion sort 
sorting_searching/insertion_sort/insertion_sort_solution.ipynb