error CS0122: 'AlembicStreamDescriptor' is inaccessible due to its protection level

Hi,

I have imported the alembic package and I am trying to do something custom with it.
However, all the classes are not public so I can't use AlembicStream for example or any other class from the package.
I think if the definition of the class in the package was something like the following it would have worked.
Is there a way to be able to use those classes in my own custom code?

Thanks for advance.