BaiduBce 
       ├── Auth                                        //BCE's signature related class 
       ├── Http                                        //BCE's Http communication related class 
       ├── Internal                                    //SDK's internal class 
       ├── Model                                       //BCE's public model class 
       ├── Services 
       │       └── Bos                                 //BOS service related class 
       │        ├── Model                           //Internal model of BOS, such as Request or Response 
       │        ├── BosClient.cs                 //BOS client entry class 
       │        └── BosConstants.cs              //Specific constant definitions for BOS, such as permission constant 
       │        └── Sts                                 //Sts certification related class 
       │        ├── Model                           //Internal model of BOS, such as Request or Response 
       │        └──  StsClient.cs                 //STS client entry class 
       ├── Util                                        //BCE's utility tool class 
       │ 
       ├── BceBaseException.cs                       //BCE base exception class 
       ├── BceClientBase.cs                          //BCE client base class 
       ├── BceClientConfiguration.cs                  //Configuration of BCE's HttpClient 
       ├── BceClientException.cs                      //Exception class of BCE's client 
       ├── BceServiceException.cs                     //The exception class after interacting with the BCE's server 
       ├── BceConstants.cs                            //Universal constants of BCE (region, request header, error code, etc.) 
       ├── DefaultRetryPolicy.cs                      //Default retry strategy 
       └── IRetryPolicy.cs                           //Retry strategy