!631 The dataset download script is missing import os in calculate_and_datagraphic.ipynb

Merge pull request !631 from lvmingfu/master

tutorials/notebook/mindinsight/calculate_and_datagraphic.ipynb

@@ -77,6 +77,7 @@
     "import urllib.request   \n",
     "from urllib.parse import urlparse\n",
     "import gzip \n",
+    "import os\n",
     "\n",
     "def unzip_file(gzip_path):\n",
     "    \"\"\"unzip dataset file\n",