pub unsafe extern "C" fn igraph_vs_size(
graph: *const igraph_t,
vs: *const igraph_vs_t,
result: *mut igraph_int_t,
) -> igraph_error_tpub unsafe extern "C" fn igraph_vs_size(
graph: *const igraph_t,
vs: *const igraph_vs_t,
result: *mut igraph_int_t,
) -> igraph_error_t