Tutorial 1: Train a Deep Q Network with TF-Agents and the use of a driver

[jan-polivka]

Hello,

I believe the tutorial 1_dqn_tutorial.ipynb has an unnecessary import of dynamic_step_driver. The module is not used at all, so the scripts runs just fine when commented out. Furthermore, I think it would be nice if the Data Collecting section explicitly talked about tutorial 4 and that this pattern is called a Driver. It is already somewhat alluding to it:

# This loop is so common in RL, that we provide standard implementations. 
# For more details see the drivers module.
# https://www.tensorflow.org/agents/api_docs/python/tf_agents/drivers

Since the tutorial on Drivers exists, it seems very handy to me to use it. Something like this:

# This loop is very common in RL, we call it a "Driver" and we provide standard implementations. 
# For more details see the tutorial 4 or the drivers module
# https://github.com/tensorflow/agents/blob/master/docs/tutorials/4_drivers_tutorial.ipynb
# https://www.tensorflow.org/agents/api_docs/python/tf_agents/drivers

It's a very minor issue but I think it's a good idea to make it simpler for learners. It would have helped me.

[ebrevdo]

Thanks! We'd love for you to submit a PR cleaning this up! It makes a great beginner contribution.