Print gene symbols instead of gene IDs, if provided.

def _init_itemid2name(self):
        """Print gene symbols instead of gene IDs, if provided."""
        if not hasattr(self.args, 'id2sym'):
            return None
        fin_id2sym = self.args.id2sym
        if fin_id2sym is not None and os.path.exists(fin_id2sym):
            id2sym = {}
            cmpl = re.compile(r'^\s*(\S+)[\s,;]+(\S+)')
            with open(fin_id2sym) as ifstrm:
                for line in ifstrm:
                    mtch = cmpl.search(line)
                    if mtch:
                        id2sym[mtch.group(1)] = mtch.group(2)
            return id2sym