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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build_wxsfile_default_gui(root):
 """ This function adds a default GUI to the wxs file """

    factory = Document()
    Product = root.getElementsByTagName('Product')[0]

    UIRef   = factory.createElement('UIRef')
    UIRef.attributes['Id'] = 'WixUI_Mondo'
    Product.childNodes.append(UIRef)

    UIRef   = factory.createElement('UIRef')
    UIRef.attributes['Id'] = 'WixUI_ErrorProgressText'
    Product.childNodes.append(UIRef)