old_contents: from gaphor.diagram.grouping import AbstractGroup, Group
  from gaphor.SysML.blocks.block import BlockItem
  from gaphor.SysML.blocks.property import PropertyItem
  
  
  @Group.register(BlockItem, PropertyItem)
  class NodeGroup(AbstractGroup):
      """
      Add node to another node.
      """
  
      def group(self):
          self.parent.subject.ownedAttribute = self.item.subject
  
      def ungroup(self):
          del self.parent.subject.ownedAttribute[self.item.subject]
  
new_contents: from gaphor.diagram.grouping import AbstractGroup, Group
  from gaphor.SysML.blocks.block import BlockItem
  from gaphor.SysML.blocks.property import PropertyItem
  
  
  @Group.register(BlockItem, PropertyItem)
  class PropertyGroup(AbstractGroup):
      """
      Add Property to a Block.
      """
  
      def group(self):
          self.parent.subject.ownedAttribute = self.item.subject
  
      def ungroup(self):
          del self.parent.subject.ownedAttribute[self.item.subject]
  
subject: Fix name for property/block group