old_contents: from kivy.factory import Factory
  
  r = Factory.register
  r('MoaStage', module='moa.stage.base')
  r('StageRender', module='moa.stage.base')
  r('Delay', module='moa.stage.delay')
  r('TreeRender', module='moa.render.treerender')
  r('TreeRenderExt', module='moa.render.treerender')
  r('StageTreeNode', module='moa.render.treerender')
  r('StageSimpleDisplay', module='moa.render.stage_simple')
  
new_contents: from kivy.factory import Factory
  
  r = Factory.register
  r('MoaStage', module='moa.stage')
  r('Delay', module='moa.stage.delay')
  r('GateStage', module='moa.stage.gate')
  
  r('StageRender', module='moa.stage.base')
  r('TreeRender', module='moa.render.treerender')
  r('TreeRenderExt', module='moa.render.treerender')
  r('StageTreeNode', module='moa.render.treerender')
  r('StageSimpleDisplay', module='moa.render.stage_simple')
  
subject: Update factory registers with stages.