code: def make_simple(self):
          
          (inner_radius, outer_radius) = self.get_radii()
          radius = (inner_radius + outer_radius) / 2
          return cadquery.Workplane('XY') \
              .circle(radius).extrude(self.length)
docs: Return a cylinder with the thread's average radius & length.
  
          :math:`radius = (inner_radius + outer_radius) / 2`