Anndata.write fails with "object header message is too large"

Hi.

I’m trying to .write() an anndata object where I have a large dataframe (8869 columns) in the obsm attribute (adata.obsm["my_key"] = large_df). The write call fails with:

RuntimeError: Unable to create attribute (object header message is too large)

Above error raised while writing key 'my_key' of <class 'h5py._hl.group.Group'> to /

Any idea if and how this can be dealt with in anndata, or must we use mudata in this case?

Thanks!