The muscle counter

A small program counts the fibres and the nuclei of a model skeletal muscle, and lists the kinds of muscle that are under the control of the will.

The idea. A muscle holds bundles. Each bundle holds the same number of fibres, and each fibre has many nuclei. The dictionary kinds gives, for each kind of muscle, whether it is striated and whether it is voluntary.

Your tasks.

1. Finish fibres_in. It gives the number of fibres.
2. Finish nuclei_in. It gives the number of nuclei.
3. Finish voluntary_kinds. It gives the list of the kinds of muscle that are voluntary.