@API(status = API.Status.STABLE)
        static <C> @NonNull Simple<C> simple(final Simple<C> filter) {
            return filter;
        }
Create a new {@link Simple}. This is a convenience method to allow
for more easily implementing {@link Simple} using a lambda without
casting, for methods which accept {@link Filter}.

@param filter filter lambda
@param <C>    sender type
@return new simple filter
cloud-core/src/main/java/org/incendo/cloud/suggestion/FilteringSuggestionProcessor.java