old_contents: from . import liftingline, nnliftingline, polarinterp
  
  from .liftingline import AirfoilData, LiftAnalysis, calculate
  
  from .aero_moment import mean_momentcoefficient
new_contents: from . import liftingline, nnliftingline
  
  from .liftingline import AirfoilData, LiftAnalysis, calculate
  
  from .aero_moment import mean_momentcoefficient
subject: fix removed polarinterp