openstudio-standards apply_prm...efficiency

edit

I'm trying to call the call the apply_prm_pressure_rise_and_motor_efficiencymethod from openstudio-standards in a measure. I included require-'openstudio-standards'in the measure.

messure snippet:

if sc.to_PumpConstantSpeed.is_initialized 
            pump = sc.to_PumpConstantSpeed.get
            pump.apply_prm_pressure_rise_and_motor_efficiency(chw_pri_only_w_per_gpm,model)

I'm getting the following error (only first line shown):

Optional not initialized :/ruby/2.2.0/gems/openstudio-standards-0.1.15/lib/openstudio-standards/standards/Standards.Pump.rb:26:in `get'

My question is whether I called the method incorrectly or the error lies within the method. If the former, my second question is how to correctly utilize the openstudio-standard methods.