text: /* */ 
  "format register";
  export class Headers {
    constructor(headers={}){
      this.headers = headers;
    }
  
    add(key, value){
      this.headers[key] = value;
    }
  
    get(key){
      return this.headers[key];
    }
  
    clear(){
      this.headers = {};
    }
  
    configureXHR(xhr){
      var headers = this.headers, key;
  
      for(key in headers){
        xhr.setRequestHeader(key, headers[key]);
      }
    }
  }
  