new_contents: from pySDC.Transfer import transfer
  from pySDC.datatype_classes.mesh import mesh, rhs_imex_mesh
  
  class mesh_to_mesh_2d(transfer):
      """
      Custon transfer class, implements Transfer.py
  
      This implementation is just a dummy for particles with no functionality. It can be used to check if in the particle
      setups the number of iterations is halved once two levels are used.
  
      Attributes:
          fine: reference to the fine level
          coarse: reference to the coarse level
          init_f: number of variables on the fine level (whatever init represents there)
          init_c: number of variables on the coarse level (whatever init represents there)
      """
  
      def __init__(self,fine_level,coarse_level,params):
          """
          Initialization routine
  
          Args:
              fine_level: fine level connected with the transfer operations (passed to parent)
              coarse_level: coarse level connected with the transfer operations (passed to parent)
          """
          super(mesh_to_mesh_2d,self).__init__(fine_level,coarse_level,params)
          pass
  
      def restrict_space(self,F):
          """
          Dummy restriction routine
  
          Args:
              F: the fine level data (easier to access than via the fine attribute)
  
          """
  
          if isinstance(F,mesh):
              G = mesh(F)
          elif isinstance(F,rhs_imex_mesh):
              G = rhs_imex_mesh(F)
          else:
              print('Transfer error')
              exit()
          return G
  
      def prolong_space(self,G):
          """
          Dummy prolongation routine
  
          Args:
              G: the coarse level data (easier to access than via the coarse attribute)
          """
  
          if isinstance(G,mesh):
              F = mesh(G)
          elif isinstance(G,rhs_imex_mesh):
              F = rhs_imex_mesh(G)
          else:
              print('Transfer error')
              exit()
          return F
subject: add transfer class for boussineqs