      "    return (balanced, min_h, max_h)\n",
      "\n",
      "def check_balance(root):\n",
      "    if root is None:\n",
      "        return False\n",
      "    balanced, _, _ = _check_balance(root)\n",
      "    return balanced"
     ]
    },
    {
 
</s> remove     "    if not root:\n",
 </s> add     "    if root is None:\n", </s> remove     "    def test_check_balance(self):\n",
    "        assert_equal(check_balance(None), False)\n",
 </s> add     "    @raises(Exception)\n",
    "    def test_check_balance_empty(self):\n",
    "        check_balance(None)\n",
    "        raise Exception('No root node')\n",
      "    return (balanced, min_h, max_h)\n",
      "\n",
      "def check_balance(root):\n",
      "    if root is None:\n",
    "        raise Exception('No root node')\n",
      "    balanced, _, _ = _check_balance(root)\n",
      "    return balanced"
     ]
    },
    {
keep keep keep keep replace keep keep keep keep keep
 Polish bst check balanced challenge and solution (#84)

Update constraints, tests, and code. 
graphs_trees/check_balance/check_balance_solution.ipynb