Ucs_stream_safeUnicode Stream Safe Format
The Unicode standard includes a specification of a stream-safe format suitable for use in constrained resource applications that would benefit from normalization. A stream-safe sequence is one that would not contain any sequences of non-starter code points of length greater than 30 when normalized to NFKD.
Use check s to consume s and return true if the sequence conforms to the stream-safe format.