Given a geneid, return the string geneid or a gene symbol.

def _get_genestr(self, itemid):
        """Given a geneid, return the string geneid or a gene symbol."""
        if itemid in self.id2symbol:
            symbol = self.id2symbol[itemid]
            if symbol is not None:
                return symbol
        if isinstance(itemid, int):
            return str(itemid)
        return itemid