fix: types

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

fixes #663

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #666 (01fccf7) into master (9a5a4c4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #666   +/-   ##
=======================================
  Coverage   90.17%   90.17%           
=======================================
  Files           2        2           
  Lines         397      397           
  Branches      119      119           
=======================================
  Hits          358      358           
  Misses         38       38           
  Partials        1        1           

Impacted Files	Coverage Δ
src/index.js	90.16% <ø> (ø)

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