code: def list_versions(self, prefix='', delimiter='', key_marker='',
                        version_id_marker='', headers=None):
          
          return VersionedBucketListResultSet(self, prefix, delimiter, key_marker,
                                              version_id_marker, headers)
docs: List version objects within a bucket.  This returns an instance of an
          VersionedBucketListResultSet that automatically handles all of the result
          paging, etc. from S3.  You just need to keep iterating until
          there are no more results.
          Called with no arguments, this will return an iterator object across
          all keys within the bucket.
          
          :type prefix: string
          :param prefix: allows you to limit the listing to a particular
                          prefix.  For example, if you call the method with
                          prefix='/foo/' then the iterator will only cycle
                          through the keys that begin with the string '/foo/'.
                          
          :type delimiter: string
          :param delimiter: can be used in conjunction with the prefix
                          to allow you to organize and browse your keys
                          hierarchically. See:
                          http://docs.amazonwebservices.com/AmazonS3/2006-03-01/
                          for more details.
                          
          :type marker: string
          :param marker: The "marker" of where you are in the result set
          
          :rtype: :class:`boto.s3.bucketlistresultset.BucketListResultSet`
          :return: an instance of a BucketListResultSet that handles paging, etc