fun <A1, R> f1(f: KFunction1<A1, R>, a1: A1): MetaFeature<R>
Creates a MetaFeature for the given function f which expects 1 argument.
Notice for assertion function writers: you should use ExpectImpl.feature and pass a
class reference instead of using this convenience function (e.g. ExpectImpl.feature(MyClass::fun, ...)).
This way we are always able to report the function name, even if the subject is not defined which occurs if a
previous transformation of the subject could not be carried out.