"Native code" label

How to detect if a function is a core part of browser API? This way:

  const a = () => {};
  a.toString(); // () => {}
  console.log.toString(); // function log() { [native code] }

You see? [native code] label. Sounds good, right?

  const a = () => {};
  const b = a.bind(null);
  b.toString(); // function () { [native code] }

Oops. But we still have this log name in the string snapshot.