Check against people who weren't paying attention.

stackoverflow-survey.ipynb

@@ -30,7 +30,12 @@
     "print(so_df.keys())\n",
     "so_df.describe()\n",
     "\n",
-    "# print(so_df[:3])"
+    "# check for people who aren't paying attention\n",
+    "count_not_apple =  (so_df[\"Check\"] != \"Apples\").sum()\n",
+    "print(count_not_apple)\n",
+    "print(so_df.shape)\n",
+    "assert(count_not_apple == 0)\n",
+    "# print(so_df[:3])\n"
    ]
   },
   {