fix tensorflow#3786

commit:7a9934d has change the matplotlib imports, it cause
object_det4ection_tutorial.ipynb to unable to run.
This commit fixes the problem.

research/object_detection/object_detection_tutorial.ipynb

@@ -33,8 +33,6 @@
     "\n",
     "from collections import defaultdict\n",
     "from io import StringIO\n",
-    "from matplotlib import pyplot as plt\n",
-    "from PIL import Image\n",
     "\n",
     "# This is needed since the notebook is stored in the object_detection folder.\n",
     "sys.path.append(\"..\")\n",
@@ -48,7 +46,29 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Env setup"
+    "## Object detection imports\n",
+    "Here are the imports from the object detection module."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "scrolled": false
+   },
+   "outputs": [],
+   "source": [
+    "from utils import visualization_utils as vis_util\n",
+    "\n",
+    "from utils import label_map_util"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Image drawing imports\n",
+    "Here are the imports for drawing the image."
    ]
   },
   {
@@ -57,16 +77,15 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# This is needed to display the images.\n",
-    "%matplotlib inline"
+    "from matplotlib import pyplot as plt\n",
+    "from PIL import Image"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Object detection imports\n",
-    "Here are the imports from the object detection module."
+    "## Env setup"
    ]
   },
   {
@@ -75,9 +94,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from utils import label_map_util\n",
-    "\n",
-    "from utils import visualization_utils as vis_util"
+    "# This is needed to display the images.\n",
+    "%matplotlib inline"
    ]
   },
   {