Allow array headers. Fixes #637

[aldenquimby]

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• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you written unit tests?
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Closing issues
Closes #637

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• Has the issue had a maintainer respond to the issue and clarify that the feature is something that aligns with the goals and philosophy of the project?

Potential Problems With The Approach

Test plan

• Unit test covers header that's an array of strings