Get Fan Associated with VRF Terminal

For a VRF terminal unit, I can access the heating or cooling coil quite simply by .heatingCoil or .coolingCoil however the method .supplyAirFan returns an HVACComponent. I can't seem to figure out how to access the fan so I can adjust the pressure rise. Moreover, the constructor for ZoneHVACTerminalUnitVariableRefrigerantFlow doesn'y allow me to pass in a fan object the way I could with ZoneHVACFourPipeFanCoil for example.

In short, what I'm wondering is how to return the fan associated with a VRF terminal unit or if there is a simple method to pass in a fan as an argument? I could just grab all the fans from the model space, but that's not quite as direct.

Here's the code I've used to get the HVAC components associated with a ZoneHVAC object.

# get equipment and components
ptac = eqpt.to_ZoneHVACPackagedTerminalAirConditioner.get

if ptac.supplyAirFan.to_FanOnOff.is_initialized
   fan = ptac.supplyAirFan.to_FanOnOff.get
elsif ptac.supplyAirFan.to_FanConstantVolume.is_initialized
   fan = ptac.supplyAirFan.to_FanConstantVolume.get
end

This is used in a measure to Rename Zone HVAC Equipment And Components available in my OpenStudio Measures repository.

# rename equipment
if rename_hvac_eqpt == true
  ptac.setName("#{z.name} PTAC")
  count_eqpt += 1
end

# rename components
if rename_hvac_comp == true
  fan.setName("#{ptac.name} Fan")
  count_fans += 1
  htg_coil.setName("#{ptac.name} Htg Coil")
  count_htg_coils += 1
  clg_coil.setName("#{ptac.name} Clg Coil")
  count_clg_coils += 1
end