set tensorflow version colab code example

Example 1: tf 1 compatible colab

Specifying the TensorFlow version
Running 

import tensorflow 

will import the default version (currently 2.x). You can use 1.x 
by running a cell with the 

%tensorflow_version 1.x

magic before you run import tensorflow.

Example 2: colab tensorflow version change

%tensorflow_version 1.x

import tensorflow
print(tensorflow.__version__)