Converting RHESSI count rate(per second per detector) to Xray Flux (W/m^{2}) using SunPy sunkit-spex

Hi. May I know if there is a way to convert the RHESSI count rate(per second per detector) to Xray Flux (W/m^{2}) in sunpy sunkit-spex? I am planning to create a timeseries of RHESSI Hard Xray Flux (W/m^{2}).