old_contents: # -*- coding: utf-8 -*-
  #
  from .surface_base import SurfaceBase
  
  
  class CompoundSurface(SurfaceBase):
      def __init__(self, surfaces):
          super(CompoundSurface, self).__init__()
          self.num_edges = sum(len(s) for s in surfaces)
  
          self.surfaces = surfaces
  
          self.code = '\n'.join([
              '{} = news;'.format(self.id),
              'Compound Surface({}) = {{{}}};'.format(
                  self.id, ','.join([s.id for s in surfaces])
              )])
          return
  
new_contents: # -*- coding: utf-8 -*-
  #
  from .surface_base import SurfaceBase
  
  
  class CompoundSurface(SurfaceBase):
      def __init__(self, surfaces):
          super(CompoundSurface, self).__init__()
          self.num_edges = sum(s.num_edges for s in surfaces)
  
          self.surfaces = surfaces
  
          self.code = '\n'.join([
              '{} = news;'.format(self.id),
              'Compound Surface({}) = {{{}}};'.format(
                  self.id, ','.join([s.id for s in surfaces])
              )])
          return
  
subject: fix CompoundSurface for new interface