问为什么使用python ruamel.yaml.dump写出的yml文件注释会丢失？

version: "3"
services:
  xxx-service:
    #测试0
    image: 192.168.0.0/xxx-service:v1.1.0
    networks:
      eureka-net:
        ipv4_address: 192.168.0.0
        aliases:
          - xxx-service
    restart: always
    #测试1
    hostname: eem-service
    #测试2
    ports:
    #测试3
    #6379: 6379
    volumes:
      # 日志数据
      - /var/log/CET/docker/eem-service/logs:/logs
      # 拓扑导出导入配置文件
      - /etc/CET/docker/config/eem-service/topology-templates:/etc/CET/eem/config/topology

# -*- coding: utf-8 -*-
#！/usr/bin/env python3
from ruamel import yaml

def up_yml():
  #读取docker-compose.yml文件
 with open('./docker-compose1.yml', 'r+', encoding="utf-8") as f:
  content = yaml.load(f, Loader=yaml.RoundTripLoader)
  #写入docker-compose.yml文件
 with open('./docker-compose2.yml', 'w+', encoding="utf-8") as nf:
   yaml.dump(content, nf,Dumper=yaml.RoundTripDumper,default_flow_style=False, allow_unicode=True, indent=2, block_seq_indent=2) 
if __name__ == '__main__':
 up_yml()

version: "3"
services:
  xxx-service:
    #测试0
    image: 192.168.0.0/xxx-service:v1.1.0
    networks:
      eureka-net:
        ipv4_address: 192.168.0.0
        aliases:
          - xxx-service
    restart: always
    #测试1
    hostname: xxx-service
    #测试2
    ports:
    #测试3
    #6379: 6379
    volumes:
      # 日志数据
      - /var/log/ABC/docker/xxx-service/logs:/logs
      # 拓扑导出导入配置文件
      - /etc/ABC/docker/config/xxx-service/topology-templates:/etc/ABC/xxx/config/topology

version: "3"
services:
  xxx-service:
    #测试0
    image: 192.168.0.0/xxx-service:v1.1.0
    networks:
      eureka-net:
        ipv4_address: 192.168.0.0
        aliases:
          - xxx-service
    restart: always
    hostname: xxx-service
    ports:
    volumes:
      # 日志数据
      - /var/log/ABC/docker/eem-service/logs:/logs
      # 拓扑导出导入配置文件
      - /etc/ABC/docker/config/xxx-service/topology-templates:/etc/ABC/xxx/config/topology