pub unsafe extern "C" fn igraph_error(
reason: *const c_char,
file: *const c_char,
line: c_int,
igraph_errno: igraph_error_t,
) -> igraph_error_tpub unsafe extern "C" fn igraph_error(
reason: *const c_char,
file: *const c_char,
line: c_int,
igraph_errno: igraph_error_t,
) -> igraph_error_t