new_contents: import MG
  
  class VarCoeffCCMG2d(MG.CellCenterMG2d):
  
      # this is a multigrid solver that supports variable coefficients
      #
      # we need to accept a coefficient array, coeffs, defined at each
      # level.  We can do this through an init_coeffs, and restrict it
      # down the MG grids once.
      #
      # we need a new compute_residual() and smooth() function, that
      # understands coeffs.
  
subject: add a new class that inherits from the MG class