Validating encoded-ness state of AnnData object

[eroell]

Description of feature

This is not an ideal way of checking whether the adata has been encoded:

ehrapy/ehrapy/anndata/anndata_ext.py

Line 325 in 3260f8f

assert np.issubdtype(adata.X.dtype, np.number)

as we do not guarantee that ep.pp.encode will enforce this typing of the array.

Think about whether to

• use a tag instead, e.g. stored in .uns
• be more clear on the dtype .X is allowed to have.

The latter option might be more clean, and could be considered a subissue of consistent use with infer feature type and