pub unsafe extern "C" fn igraph_dfs(
graph: *const igraph_t,
root: igraph_int_t,
mode: igraph_neimode_t,
unreachable: igraph_bool_t,
order: *mut igraph_vector_int_t,
order_out: *mut igraph_vector_int_t,
parents: *mut igraph_vector_int_t,
dist: *mut igraph_vector_int_t,
in_callback: igraph_dfshandler_t,
out_callback: igraph_dfshandler_t,
extra: *mut c_void,
) -> igraph_error_t