Readability edits, bug fix. (#962)

* Readability edits, bug fix.

Fix bug in "Use location of relevant objects to call functions and perform pick-and-place". Write prompts in a consistent way using textwrap.dedent, clean up imports, remove unused code, fix misc errors in exceptions, autoformat.

Reran entire notebook, output quality seems the same although the prompts have some subtle changes and additional newlines.

"Pointing to Defined Objects in a GIF" gets stuck sometimes but happens in the original notebook too, feels like server-side issue?

* Apply tensorflow_docs.tools.nbfmt

Author: williamito