Return node position(integer) for a given key. Else return None

def _get_node_pos(self, key):
        """
            Return node position(integer) for a given key. Else return None
        """
        if not self._hashring:
            return None

        key = self._gen_key(key)

        nodes = self._sorted_keys
        pos = bisect(nodes, key)

        if pos == len(nodes):
            return 0
        return pos