/usr/include/seqan/stream/ is in libseqan2-dev 2.3.1+dfsg-4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/seqan/stream/adapt_ios.h
/usr/include/seqan/stream/buffered_stream.h
/usr/include/seqan/stream/file_stream.h
/usr/include/seqan/stream/formatted_file.h
/usr/include/seqan/stream/guess_format.h
/usr/include/seqan/stream/iostream_bgzf.h
/usr/include/seqan/stream/iostream_bzip2.h
/usr/include/seqan/stream/iostream_bzip2_impl.h
/usr/include/seqan/stream/iostream_zip.h
/usr/include/seqan/stream/iostream_zip_impl.h
/usr/include/seqan/stream/iostream_zutil.h
/usr/include/seqan/stream/iter_stream.h
/usr/include/seqan/stream/lexical_cast.h
/usr/include/seqan/stream/stream_base.h
/usr/include/seqan/stream/stream_compressor.h
/usr/include/seqan/stream/tokenization.h
/usr/include/seqan/stream/virtual_stream.h