I want to use the UnmodifiableListMixin from the Dart internal library, is it possible to import it in any way?
I see that other "dart:X" libraries use the ```import "dart:_internal"``` statement for that, but is does not seem to work.
If it is possible, I'd like to know how, and if it is not, I'd like to know if the license of that code allows me to just copy it into my project (it's licensed with standard MIT license).
Thanks
Steven