Reports any uses of java.util.Optional<T>, java.util.OptionalDouble, java.util.OptionalInt or
java.util.OptionalLong as the type for a field or a parameter.
Optional was designed to provide a limited mechanism for library method return types where there needed
to be a clear way to represent "no result".
Using a field with type Optional is also problematic if the class needs to be Serializable, which Optional isn't.
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