Man pages matching name gnutls_session_set_verify_cert2 in section 3:

gnutls_session_set_verify_cert2.3.en	debian 10 / gnutls-doc
gnutls_session_set_verify_cert2.3.en	debian 11 / gnutls-doc
gnutls_session_set_verify_cert2.3.en	debian 12 / gnutls-doc