This function should only ever see a single label (x)
and a single notation.
strip_label_part(x, notation, part, pattern_pref = "", pattern_suff = "")A label shorn of the part to be stripped.
The label(s) to be split.
The notations to be used for each x.
The part of the label to work on, such as "pref_start", "pref_end", "suff_start", or "suff_end".
The prefix to a regex pattern to be used in gsub().
The suffix to a regex pattern to be used in gsub().
If notation is NULL, x is returned, unmodified.