feat: return conversion function

[nstarman]

Allows for the conversion function to be used after being registered.

[coveralls]

Pull Request Test Coverage Report for Build 8334297765

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 97.731%

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Totals
Change from base Build 7600638892:	0.002%
Covered Lines:	1335
Relevant Lines:	1366

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💛 - Coveralls

[wesselb]

Hey @nstarman! Very sensible. Thanks for the contribution. Merging this right away. :)