Function igraph_sparsemat_index 

pub unsafe extern "C" fn igraph_sparsemat_index(
    A: *const igraph_sparsemat_t,
    p: *const igraph_vector_int_t,
    q: *const igraph_vector_int_t,
    res: *mut igraph_sparsemat_t,
    constres: *mut igraph_real_t,
) -> igraph_error_t