cellViewNamespace - this option can be used to change the default behavior of JointJS which by default reads cell view definitions from the joint.shapes namespace. For example, if a cell is of type 'myshapes.MyElement', then the paper looks up joint.shapes.myshapes.MyElementView object type when rendering the cell onto the screen. If cellViewNamespace is set, the paper will read the view definition from the myShapesNamespace.myshapes.MyElementView object instead. This is useful in situations where you - for any reason - don't want to use the joint.shapes namespace for defining your own custom shapes. This option is often used in combination with cellNamespace option on the joint.dia.Graph object.