def list(
            self,
            bucket: str,
            prefix: str=None,
            delimiter: str=None,
    ) -> typing.Iterator[str]:
        """
        Returns an iterator of all blob entries in a bucket that match a given prefix.  Do not return any keys that
        contain the delimiter past the prefix.
        """
        kwargs = dict()
        if prefix is not None:
            kwargs['Prefix'] = prefix
        if delimiter is not None:
            kwargs['Delimiter'] = delimiter
        for item in (
                boto3.resource("s3").Bucket(bucket).
                objects.
                filter(**kwargs)):
            yield item.key