Trailing spaces in column attributes

[HenriettaHolze]

Hi,

It seems like some column attributes have trailing white space, e.g. the Roi "Human A25". When reading the loom file with SeuratDisk this is apparent but not when reading the file with loompy. I'm not entirely sure whether it is a SeuratDisk bug or loompy automatically strips the column attributes. This could lead to problems when subsetting the atlas to certain regions with any other tool than loompy.