old_contents: from bikewheelfem import BicycleWheelFEM
  from femsolution import FEMSolution
  from rigidbody import RigidBody
  from spokesection import SpokeSection
  from rimsection import RimSection
  from wheelgeometry import WheelGeometry
  from helpers import *
  
new_contents: from bicycle_wheel import BicycleWheel
  from bikewheelfem import BicycleWheelFEM
  from femsolution import FEMSolution
  from rigidbody import RigidBody
  from helpers import *
  
subject: remove old classes