def scan(self, cursor=0, match=None, count=None):
        """Incrementally iterate the keys space.

        Usage example:

        >>> match = 'something*'
        >>> cur = b'0'
        >>> while cur:
        ...     cur, keys = await redis.scan(cur, match=match)
        ...     for key in keys:
        ...         print('Matched:', key)

        """
        args = []
        if match is not None:
            args += [b'MATCH', match]
        if count is not None:
            args += [b'COUNT', count]
        fut = self.execute(b'SCAN', cursor, *args)
        return wait_convert(fut, lambda o: (int(o[0]), o[1]))