code: def add_task_group(self, task_group, project):
          
          route_values = {}
          if project is not None:
              route_values['project'] = self._serialize.url('project', project, 'str')
          content = self._serialize.body(task_group, 'TaskGroupCreateParameter')
          response = self._send(http_method='POST',
                                location_id='6c08ffbf-dbf1-4f9a-94e5-a1cbd47005e7',
                                version='5.0-preview.1',
                                route_values=route_values,
                                content=content)
          return self._deserialize('TaskGroup', response)
docs: AddTaskGroup.
          [Preview API] Create a task group.
          :param :class:`<TaskGroupCreateParameter> <azure.devops.v5_0.task_agent.models.TaskGroupCreateParameter>` task_group: Task group object to create.
          :param str project: Project ID or project name
          :rtype: :class:`<TaskGroup> <azure.devops.v5_0.task_agent.models.TaskGroup>`