"AnnData.concatenate" discards parts of the .raw attribute

[watiss]

In reference to #263

I am facing a similar issue now. I am concatenating two identical anndatas (as a test). They have the same var dataframe under adata.raw.var and adata2.raw.var. However, adata3, which is the results of adata3 = adata.concatenate(adata2, join="outer") has a dataframe in adata3.raw.var that is missing the columns (only the index is there). Is this expected?