Add type check for stored sign. Resolves #62
Add type check for stored sign. Resolves #62

Multiple users reported problems related to the `dtype` of `sign` in
stored `h5` files. The possible `dtype`s are `byte` and `str`, which
is now checked for.

Also closes this comment:
https://github.com/jniediek/combinato/issues/60#issuecomment-983086845

jniediek/combinato