Add comment explaining what the predicted output format.

samples/2.5 [Numeric] Learning-to-Rank with Microsoft Bing Data.ipynb

@@ -301,6 +301,7 @@
     "import pandas as pd\n",
     "scores[['Relevance','QueryID']] = pd.read_csv(test_file, header = None)[[0,1]]\n",
     "\n",
+    "# Show the top 10 predicted items for query 5.\n",
     "print(\"Prediction scores: \")\n",
     "scores[scores.QueryID == 5].sort_values('Score', ascending=False).head(10)"
    ]