'Given a string key a corresponding node in the hash ring is returned
along with it\'s position in the ring.
If the hash ring is empty, (`None`, `None`) is returned.'

def get_node_pos(self, string_key):

    if (not self.ring):
        return None
    key = self.gen_key(string_key)
    nodes = self._sorted_keys
    pos = bisect(nodes, key)
    if (pos == len(nodes)):
        return 0
    else:
        return pos
