Man pages matching name ne_set_session_flag in section 3:

ne_set_session_flag.3.en	debian 10 / libneon27-dev
ne_set_session_flag.3.en	debian 10 / libneon27-gnutls-dev
ne_set_session_flag.3.en	debian 11 / libneon27-dev
ne_set_session_flag.3.en	debian 11 / libneon27-gnutls-dev
ne_set_session_flag.3.en	debian 12 / libneon27-dev
ne_set_session_flag.3.en	debian 12 / libneon27-gnutls-dev