code: @SuppressWarnings("unused")
      public static Completable save(String path, String data) {
          Map<String, Object> map = new HashMap<String, Object>() {{
              put("path", path);
              put("data", data);
          }};
          return SingleRxXian.call("cosService", "cosWrite", map).toCompletable();
      }
docs: 保存文件到云上，阻塞直到保存成功返回
  
  @param path 文件相对路径
  @param data 文件内容
  @return successful/unsuccessful unit response