S3BucketBaseReader strange iter behavior

[thorwhalen]

from py2store import myconfigs
from py2store.persisters.new_s3 import S3BucketBaseReader

ro_client_kwargs = myconfigs['my_configs_for_this.ini']['s3_all_ro']
s = S3BucketBaseReader(ro_client_kwargs, 'otodata')

>>> list(s)
['/', 'cf-templates/', 'indices/', 'lib/', 'odir/', 'something_else/']

What's that '?' key doing there. What's in it?

>>> list(s['/'])
['/indices/', '/odir/']

Curiouser and curiouser! We get indices and odir... but not the other ones?!?!