code: def fullselection(self) -> selectiontools.Selection:
          
          fullselection = selectiontools.Selection('fullselection')
          for selection in self.selections:
              fullselection += selection
          fullselection += self.devices
          return fullselection
docs: A |Selection| object containing all |Element| and |Node| objects
          defined by |XMLInterface.selections| and |XMLInterface.devices|.
  
          >>> from hydpy.core.examples import prepare_full_example_1
          >>> prepare_full_example_1()
  
          >>> from hydpy import HydPy, TestIO, XMLInterface
          >>> hp = HydPy('LahnH')
          >>> with TestIO():
          ...     hp.prepare_network()
          ...     interface = XMLInterface('single_run.xml')
          >>> interface.find('selections').text = 'nonheadwaters'
          >>> interface.fullselection
          Selection("fullselection",
                    nodes=("dill", "lahn_2", "lahn_3"),
                    elements=("land_dill", "land_lahn_1", "land_lahn_2",
                              "land_lahn_3"))