Nice to have - setting values back to system from time series data for a specific time step

[rbolgaryn]

# This cannot work because we do not know the redistribution keys from the power values of devices 
# to the power values of buses. Leaving this here anyways to document this issue.
function set_system_time_step(sys::PSY.System, data::PowerFlowData; time_step = 1)
    @error("This function cannot work")
    for bus in PSY.get_components(PSY.Bus, sys)
        bus_number = data.bus_lookup[PSY.get_number(bus)]
        bus_type = data.bus_type[bus_number, time_step]
        sys_bus_type = sys.bustype # here we should be using the system bus type to know which inputs to modify

        # for REF bus, we don't need to set anything
        if sys_bus_type == PSY.ACBusTypes.PV
            # we need to modify the P value
            # TODO if we also modify time-series data for voltage set-points, also set that value. 
            #  However, we cannot do this easily because it can happen that the PV -> PQ transformation 
            #  caused a different Vm value as the result, while the set-point Vm is still the same. 
            #  We need a solution for this.
            P_gen = data.bus_activepower_injection[bus_number, time_step]
            Q_gen = 0.0
            # TODO write time-series value of the bus back to devices (not possible)
        elseif sys_bus_type == PSY.ACBusTypes.PQ
            P_gen = data.bus_activepower_injection[bus_number, time_step]
            Q_gen = data.bus_reactivepower_injection[bus_number, time_step]
            P_load = data.bus_activepower_withdrawals[bus_number, time_step]
            Q_load = data.bus_reactivepower_withdrawals[bus_number, time_step]
            # TODO write time-series value of the bus back to devices (not possible)
        end
    end
end