fix typo 'in' operator

Fixed a small typo in the negative 'in' test operator
minor #1260 fix typo 'in' operator (thewholelifetolearn)

This PR was merged into the master branch.

Discussion
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fix typo 'in' operator

Fixed a small typo in the negative 'in' test operator

Commits
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f9013d5 fix typo 'in' operator