Function pio_nodal_demand 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pio_nodal_demand(
    net: *const PioNetwork,
    pd: *mut f64,
    qd: *mut f64,
)

Fill nodal aggregates (each length pio_n_buses, dense order): active and reactive demand summed per bus. Any pointer may be NULL.