old_contents: import defcon
  from fontParts.base import BaseKerning, FontPartsError
  from fontParts.nonelab.base import RBaseObject
  
  
  class RKerning(RBaseObject, BaseKerning):
  
      def _items(self):
          return self.naked().items()
  
      def _contains(self, key):
          return key in self.naked()
  
      def _setItem(self, key, value):
          self.naked()[key] = value
  
      def _getItem(self, key):
          return self.naked()[key]
  
      def _delItem(self, key):
          del self.naked()[key]
  
new_contents: import defcon
  from fontParts.base import BaseKerning, FontPartsError
  from fontParts.nonelab.base import RBaseObject
  
  
  class RKerning(RBaseObject, BaseKerning):
  
      wrapClass = defcon.Kerning
  
      def _items(self):
          return self.naked().items()
  
      def _contains(self, key):
          return key in self.naked()
  
      def _setItem(self, key, value):
          self.naked()[key] = value
  
      def _getItem(self, key):
          return self.naked()[key]
  
      def _delItem(self, key):
          del self.naked()[key]
  
subject: Define the wrap class.