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 self.id2symbol is not None:
            symbol = self.id2symbol.get(itemid, None)
            if symbol is not None:
                return symbol
        if isinstance(itemid, int):
            return str(itemid)
        return itemid