请介绍中国的环渤海经济圈，包括其覆盖的省份和市以及其经济发展特点
user
{
  "coverage": {
    "provinces": ["河北省", "山东省", "辽宁省", "天津市", "北京市"],
    "cities": ["石家庄", "济南", "沈阳", "天津", "北京"]
  },
  "economic_features": {
    "industrial_diversity": "涵盖了重工业、轻工业、服务业等多个领域",
    "trade_importance": "是中国重要的对外贸易门户，拥有多个大型港口",
    "infrastructure": "拥有发达的交通网络，包括高速公路、铁路和航空",
    "regional_cooperation": "区域内城市间合作紧密，形成了互补性强的经济体系"
  }
}
assistant