@NonNull
        @Override
        public Function<T, R> unwrap() {
            return fn;
        }
wrap {@link Function} to TTL wrapper.

@param fn input {@link Function}
@return Wrapped {@link Function}
@see TtlUnwrap#unwrap(Object)
@since 2.11.4
@deprecated overload methods using the same name {@code wrap} is not readable
and have the type inference problems in some case;
so use {@link TtlWrappers#wrapFunction(Function)} instead.
ttl2-compatible/src/main/java/com/alibaba/ttl/TtlWrappers.java