doc(preprocessor): update documentation

[pythonbrad]

Linked to

• Update the afrim-preprocesor documentation #155

[coveralls]

Pull Request Test Coverage Report for Build 7807190386

Warning: This coverage report may be inaccurate.

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A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.788%

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Totals
Change from base Build 7806466042:	0.0%
Covered Lines:	1467
Relevant Lines:	1485

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💛 - Coveralls