fix bug：AttributeError: module 'tensorflow' has no attribute 'sub'

Signed-off-by: atian <lai@atian.me>

Author: atian

01_Introduction/05_Declaring_Operations/05_operations.ipynb

@@ -61,9 +61,7 @@
   {
    "cell_type": "code",
    "execution_count": 3,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -91,9 +89,7 @@
   {
    "cell_type": "code",
    "execution_count": 4,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -117,9 +113,7 @@
   {
    "cell_type": "code",
    "execution_count": 5,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -145,9 +139,7 @@
   {
    "cell_type": "code",
    "execution_count": 6,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -179,9 +171,7 @@
   {
    "cell_type": "code",
    "execution_count": 7,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -196,7 +186,7 @@
     "\n",
     "def custom_polynomial(x_val):\n",
     "    # Return 3x^2 - x + 10\n",
-    "    return(tf.sub(3 * tf.square(x_val), x_val) + 10)\n",
+    "    return(tf.subtract(3 * tf.square(x_val), x_val) + 10)\n",
     "\n",
     "print(sess.run(custom_polynomial(11)))"
    ]
@@ -211,9 +201,7 @@
   {
    "cell_type": "code",
    "execution_count": 8,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -238,9 +226,7 @@
   {
    "cell_type": "code",
    "execution_count": 9,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -286,7 +272,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.5.2"
+   "version": "3.5.5"
   }
  },
  "nbformat": 4,