Make export function preserve types

[adamnovak]

Motivation

This should fix #665.

Approach

I made the @export annotation function generic so it returns the same type as its input.

Checklist

• Add appropriate test(s) to the automatic suite
• Use make pretty to reformat the code with black
• Use make check to statically check the code using Pyre and Pylint
  Does not work, pyre-check==0.0.27 is required according to requirements-dev.txt, which is not available for any Python newer than 3.6, which ended security support on 23 Dec 2021. Current pyre-check versions do not have the --show-parse-errors option used in the script.
• Send PR from a dedicated branch without unrelated edits
• Ensure compatibility with this project's MIT license

[coveralls]

Pull Request Test Coverage Report for Build 7230689392

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 95.191%

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Totals
Change from base Build 6923130559:	0.03%
Covered Lines:	7363
Relevant Lines:	7735

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💛 - Coveralls

[mlin]

Thanks @adamnovak! The repo definitely needs some modernization of all the supporting tooling in the coming year. Building an agenda in #668