Inquiries about boiler costs

Hello, if I use code ```CHP_sys = create_coheat_and_power_system(combustible_slurries=a, combustible_gases=b, mockup=True, satisfy_system_electricity_demand=False)``` when calling the boiler, that is the boiler does not produce electricity. If the boiler does not produce electricity, the generator cost should not be included, but BioSTEAM does include it by default (https://github.com/BioSTEAMDevelopmentGroup/biosteam/blob/master/biosteam/facilities/_boiler_turbogenerator.py#L17-L29). Could I consult you what code can I use to exclude the generator cost?

Start with the create_coheat_and_power_system call in the issue and inspect BioSTEAM's biosteam/facilities/_boiler_turbogenerator.py lines 17-29. Trace how mockup and satisfy_system_electricity_demand affect boiler costs, then identify the configuration that excludes generator cost when no electricity is produced. Done means the relevant scenario no longer includes that cost.

Written by the indexing model from the issue text.