Issue #3522955: add attribute classes.

Closes #3522955

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• 7211248f - Issue #3522955: convert plugins and some minor cleanup.

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• 0cece31f - Issue #3522955: update the managers.

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• 5c7948cb - Issue #3522955: add the provider arg.

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changed title from Issue #3522955: add annotation classes. to Issue #3522955: add attribute classes.