Enforce Lightning module as source of truth for automatic optimization

[ananthsub]

What does this PR do?

This is further cleanup from #4317. This PR deletes the train loop's automatic optimization attribute and enforces all accesses go through the lightning module's property. This ensures we don't have divergence across these fields. Since the lightning module is the sole decider for automatic optimization, it looked very odd that the lightning module itself was referring to this property via self.trainer.train_loop.automatic_optimization even though self.automatic_optimization was already defined. Now that the trainer constructor argument for automatic_optimization is gone, we can simplify this.

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[pep8speaks]

Hello @ananthsub! Thanks for updating this PR.

• In the file pytorch_lightning/trainer/training_loop.py:

Line 719:13: W503 line break before binary operator

Comment last updated at 2021-04-26 05:15:17 UTC

[codecov]

Codecov Report

Merging #7130 (4a414dd) into master (44d775f) will decrease coverage by 4%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #7130    +/-   ##
=======================================
- Coverage      91%     87%    -4%     
=======================================
  Files         198     198            
  Lines       12635   12632     -3     
=======================================
- Hits        11541   11008   -533     
- Misses       1094    1624   +530     

[SeanNaren]

thanks @ananthsub :)

[tchaton]

Really neat !