hemilist.unwrap: Unwrap hemi data from a named hemi list.
In neuroconductor/fsbrain: Managing and Visualizing Brain Surface Data

Unwrap hemi data from a named hemi list.

1	hemilist.unwrap(hemi_list, hemi = NULL, allow_null_list = FALSE)

`hemi_list`	named list, can have entries 'lh' and/or 'rh'
`hemi`	character string, the hemi data name to retrieve from the list. Can be NULL if the list only has a single entry.
`allow_null_list`	logical, whether to silently return NULL instead of raising an error if 'hemi_list' is NULL