`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.