Function igraph_strength 

pub unsafe extern "C" fn igraph_strength(
    graph: *const igraph_t,
    res: *mut igraph_vector_t,
    vids: igraph_vs_t,
    mode: igraph_neimode_t,
    loops: igraph_loops_t,
    weights: *const igraph_vector_t,
) -> igraph_error_t