replace activation strings with tf functions

samples/core/get_started/_index.ipynb

@@ -154,7 +154,7 @@
     },
     {
       "metadata": {
-        "id": "rBO43XtLjhCd",
+        "id": "h3IKyzTCDNGo",
         "colab_type": "code",
         "colab": {
           "autoexec": {
@@ -167,12 +167,12 @@
       "source": [
         "model = tf.keras.models.Sequential([\n",
         "  tf.keras.layers.Flatten(),\n",
-        "  tf.keras.layers.Dense(512, activation='relu'),\n",
+        "  tf.keras.layers.Dense(512, activation=tf.nn.relu),\n",
         "  tf.keras.layers.Dropout(0.2),\n",
-        "  tf.keras.layers.Dense(10, activation='softmax')\n",
+        "  tf.keras.layers.Dense(10, activation=tf.nn.softmax)\n",
         "])\n",
         "\n",
-        "model.compile(optimizer='adam', \n",
+        "model.compile(optimizer='adam',\n",
         "              loss='sparse_categorical_crossentropy',\n",
         "              metrics=['accuracy'])"
       ],
@@ -191,7 +191,7 @@
     },
     {
       "metadata": {
-        "id": "cQnPHobsj0td",
+        "id": "F7dTAzgHDUh7",
         "colab_type": "code",
         "colab": {
           "autoexec": {
@@ -216,7 +216,7 @@
       },
       "cell_type": "markdown",
       "source": [
-        "That’s it! You’ve just trained an image classifier with ~98% accuracy on this dataset. See [Get Started with TensorFlow](https://www.tensorflow.org/get_started/) to learn more."
+        "You’ve now trained an image classifier with ~98% accuracy on this dataset. See [Get Started with TensorFlow](https://www.tensorflow.org/get_started/) to learn more."
       ]
     }
   ]