Man pages matching name gnutls_tdb_set_store_func in section 3:

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