code: def _body_builder(self, kwargs):
          
          p = {
              'action_name': self.name,
              'service_type': self.service_type,
              'arguments': '',
              }
          if kwargs:
              arguments = [
                  self.argument_template % {'name': k, 'value': v}
                  for k, v in kwargs.items()
              ]
              p['arguments'] = ''.join(arguments)
          body = self.body_template.strip() % p
          return body
docs: Helper method to construct the appropriate SOAP-body to call a
          FritzBox-Service.