docs: def destroy_digidoc_session(self):
          """ Closes DigiDocService session and clears request.session[I{DIGIDOC_SESSION_KEY}]
          """
  
          # cleanup data too
          self.destroy_digidoc_session_data()
  
          try:
              session = self.request.session[self.DIGIDOC_SESSION_KEY]
  
              if session:
                  try:
                      service = self.flat_service()
                      service.session_code = session
                      service.close_session()
  
                  except DigiDocError:
                      pass
  
              del self.request.session[self.DIGIDOC_SESSION_KEY]
  
          except KeyError:
              pass