Set Dynamic Modeler Attributes with python

I am using the Dynamic Modeler Module in my python script.
For the ROI Cut Tool, I set the input model, input ROI and output model and so far this works perfectly.
But I want the surface to be capped. In the Dynamic Modeler widget there is an option “Cap surface” with a checkbox. How can I set this attribute with python?
I figured out how to set the attributes:

dynamicModelerNode.SetAttribute(“ROICut.CapSurface”, _ )

but what value do i need to put to make it work? It only takes a string.

I tried finding the attributes with their possible values like this:

roiCutTool = slicer.vtkSlicerDynamicModelerROICutTool()
for i in range(roiCutTool.GetNumberOfInputParameters()):

but for the possible values of ROICut.CapSurface, it returns None.

This should work:

dynamicModelerNode.SetAttribute('ROICut.CapSurface', '1')

FYI the way I found it out was that I printed the content of the ROI cut parameter node. It gave me this:

>>> print(dynamicModelerNode)
vtkMRMLDynamicModelerNode (0000026506838D10)
  ID: vtkMRMLDynamicModelerNode1
  ClassName: vtkMRMLDynamicModelerNode
  Name: ROI cut
  Debug: false
  MTime: 278225
  Description: (none)
  SingletonTag: (none)
  HideFromEditors: false
  Selectable: true
  Selected: false
  UndoEnabled: false
  Node references:
    ROICut.InputModel: (none)
    ROICut.InputROI: (none)
    ROICut.OutputNegativeModel: (none)
    ROICut.OutputPositiveModel: (none)
  ToolName: ROI cut
  ContinuousUpdate: false