      "def main():\n",
      "    test = TestBstValidate()\n",
      "    test.test_bst_validate()\n",
      "\n",
      "\n",
      "if __name__ == '__main__':\n",
      "    main()"
     ]
 
</s> remove     "def __validate_bst__(node, mininum, maximum):\n",
 </s> add     "def _validate_bst(node, mininum, maximum):\n", </s> remove     "    return __validate_bst__(node, None, None)\n",
 </s> add     "    if node is None:\n",
    "        raise Exception('No root node')\n",
    "    return _validate_bst(node, None, None)\n",
    "    test.test_bst_validate_empty()\n",
      "def main():\n",
      "    test = TestBstValidate()\n",
    "    test.test_bst_validate_empty()\n",
      "    test.test_bst_validate()\n",
      "\n",
      "\n",
      "if __name__ == '__main__':\n",
      "    main()"
     ]
keep add keep keep keep keep keep keep
 Polish bst validate challenge and solution (#83)

Update constraints, test cases, tests, algorithm discussion, and code. 
graphs_trees/bst_validate/bst_validate_solution.ipynb