old_contents: from sfa.rspecs.elements.element import Element
  
  class Sliver(Element):
      fields = [
          'sliver_id',
          'component_id',
          'client_id',
          'name',
          'type',
          'tags',
      ]
  
new_contents: from sfa.rspecs.elements.element import Element
  
  class Sliver(Element):
      fields = [
          'sliver_id',
          'component_id',
          'client_id',
          'name',
          'type',
          'tags',
          'disk_images',
      ]
  
subject: add 'disk_images' to fields