/usr/include/boost/optional/ is in libboost1.62-dev 1.62.0+dfsg-5.
This file is owned by root:root, with mode 0o755.
..
/usr/include/boost/optional/bad_optional_access.hpp
/usr/include/boost/optional/detail/
/usr/include/boost/optional/detail/old_optional_implementation.hpp
/usr/include/boost/optional/detail/optional_aligned_storage.hpp
/usr/include/boost/optional/detail/optional_config.hpp
/usr/include/boost/optional/detail/optional_factory_support.hpp
/usr/include/boost/optional/detail/optional_reference_spec.hpp
/usr/include/boost/optional/detail/optional_relops.hpp
/usr/include/boost/optional/detail/optional_swap.hpp
/usr/include/boost/optional/optional.hpp
/usr/include/boost/optional/optional_fwd.hpp
/usr/include/boost/optional/optional_io.hpp