Man pages matching name gearman_client_set_created_fn in section 3:

gearman_client_set_created_fn.3.en	debian 10 / libgearman-dev
gearman_client_set_created_fn.3.en	debian 11 / libgearman-dev
gearman_client_set_created_fn.3.en	debian 12 / libgearman-dev