Update data_performance.ipynb

Final copy of change

Author: RenuPatelGoogle

site/en/guide/data_performance.ipynb

@@ -135,7 +135,7 @@
         "id": "3bU5gsSI-jKF"
       },
       "source": [
-        " The dataset\n",
+        "### The dataset\n",
         "\n",
         "Start with defining a class inheriting from `tf.data.Dataset` called `ArtificialDataset`.\n",
         "This dataset:\n",
@@ -187,7 +187,7 @@
         "id": "FGK1Y4jn-jKM"
       },
       "source": [
-        " The training loop\n",
+        "### The training loop\n",
         "\n",
         "Next, write a dummy training loop that measures how long it takes to iterate over a dataset.\n",
         "Training time is simulated."
@@ -227,7 +227,7 @@
         "id": "Xi8t26y7-jKV"
       },
       "source": [
-        " The naive approach\n",
+        "### The naive approach\n",
         "\n",
         "Start with a naive pipeline using no tricks, iterating over the dataset as-is."
       ]