code: def neighbors(geohash):
    
    return {
      'n':  adjacent(geohash, 'n'),
      'ne': adjacent(adjacent(geohash, 'n'), 'e'),
      'e':  adjacent(geohash, 'e'),
      'se': adjacent(adjacent(geohash, 's'), 'e'),
      's':  adjacent(geohash, 's'),
      'sw': adjacent(adjacent(geohash, 's'), 'w'),
      'w':  adjacent(geohash, 'w'),
      'nw': adjacent(adjacent(geohash, 'n'), 'w'),
      'c':  geohash
    }
docs: Return all neighboring geohashes.