What is (or could be) the use of `annotation_classes` in `create_key` ?

[neurorepro]

Summary

It would be great to know what the intended use, and/or what could be the alternate use of the parameter annotation_classes in the function create_key.

Platform details:

• Heudiconv version:

$ heudiconv --version
0.9.0

[asmacdo]

It seems to us that annotation_classes is not used. IMO, this should be removed.

However, since there is a 3rd create_key argument in use everywhere, I've created a 1.0 milestone. We should remove this whenever we are making other backwards incompatible changes to minimize disruption.