code: func hasCustomUnmarshaler(t reflect.Type) bool {
  	t = reflect.PtrTo(t)
  	return t.Implements(reflect.TypeOf((*easyjson.Unmarshaler)(nil)).Elem()) ||
  		t.Implements(reflect.TypeOf((*json.Unmarshaler)(nil)).Elem()) ||
  		t.Implements(reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem())
  }
docs: // returns true of the type t implements one of the custom unmarshaler interfaces