Sort coloredmeshes into 2 lists by their 'hemi' property.
# S3 method for coloredmeshes.by.hemi
sort(coloredmeshes)
list of coloredmeshes or other renderables
named list with two entries: "lh": list of coloredmeshes that have property hemi set to 'lh'. "rh": list of coloredmeshes that have property hemi set to 'rh'. The rest is ignored.