@deftypefun {void} {gnutls_pubkey_set_pin_function} (gnutls_pubkey_t @var{key}, gnutls_pin_callback_t @var{fn}, void * @var{userdata})
@var{key}: A key of type @code{gnutls_pubkey_t} 

@var{fn}: the callback

@var{userdata}: data associated with the callback

This function will set a callback function to be used when
required to access the object. This function overrides any other
global PIN functions.

Note that this function must be called right after initialization
to have effect.

@strong{Since:} 3.1.0
@end deftypefun