code: def add_deployment_group(self, deployment_group, project):
          
          route_values = {}
          if project is not None:
              route_values['project'] = self._serialize.url('project', project, 'str')
          content = self._serialize.body(deployment_group, 'DeploymentGroupCreateParameter')
          response = self._send(http_method='POST',
                                location_id='083c4d89-ab35-45af-aa11-7cf66895c53e',
                                version='5.1-preview.1',
                                route_values=route_values,
                                content=content)
          return self._deserialize('DeploymentGroup', response)
docs: AddDeploymentGroup.
          [Preview API] Create a deployment group.
          :param :class:`<DeploymentGroupCreateParameter> <azure.devops.v5_1.task_agent.models.DeploymentGroupCreateParameter>` deployment_group: Deployment group to create.
          :param str project: Project ID or project name
          :rtype: :class:`<DeploymentGroup> <azure.devops.v5_1.task-agent.models.DeploymentGroup>`