class_docstr: A DummyVertex is used for edges that span over several layers, it's inserted in every inner layer.
  
  **Attributes**
      - view (viewclass): since a DummyVertex is acting as a Vertex, it must have a view.
      - ctrl (list[_sugiyama_attr]): the list of associated dummy vertices.
code: def __init__(self, r=None):
      self.view = Rectangle()
      self.control_vertices = None
      super().__init__(r, is_dummy=1)
  
file_path: pygraphistry/graphistry/layout/utils/dummyVertex.py
imports: from .rectangle import Rectangle
  from .layoutVertex import LayoutVertex
label_desc: Use image node_id 1 to create a new DummyVertex object from inherited base classes: LayoutVertex with example: obj = DummyVertex(r)