Man pages matching name mongoc_client_session_get_opts in section 3:

mongoc_client_session_get_opts.3.en	debian 10 / libmongoc-doc
mongoc_client_session_get_opts.3.en	debian 11 / libmongoc-doc
mongoc_client_session_get_opts.3.en	debian 12 / libmongoc-doc