code: def _get_version(self):
          
          version = self._get_param(param="version", allowed_values=allowed_versions[self.params['service']],
                                    optional=True)
          if version is None and self._get_request_type() != "getcapabilities":
              raise OWSMissingParameterValue('Parameter "version" is missing', value="version")
          else:
              return version
docs: Find requested version in GET request.