old_contents: def setup():
      from .qt_widget import DendroWidget
      from glue.config import qt_client
      qt_client.add(DendroWidget)
  
new_contents: def setup():
      from glue.config import qt_client
      from .qt_widget import DendroWidget
      from .data_factory import load_dendro
      qt_client.add(DendroWidget)
  
subject: Add missing import of dendrogram data factory