code: def _new_theme_part(cls, package):
          
          partname = package.next_partname('/ppt/theme/theme%d.xml')
          content_type = CT.OFC_THEME
          theme = CT_OfficeStyleSheet.new_default()
          return XmlPart(partname, content_type, theme, package)
docs: Create and return a default theme part suitable for use with a notes
          master.