code: def _get_service(self):
          
          if "service" in self.document.attrib:
              value = self.document.attrib["service"].lower()
              if value in allowed_service_types:
                  self.params["service"] = value
              else:
                  raise OWSInvalidParameterValue("Service %s is not supported" % value, value="service")
          else:
              raise OWSMissingParameterValue('Parameter "service" is missing', value="service")
          return self.params["service"]
docs: Check mandatory service name parameter in POST request.