Write tests, improve API, create documentation

src/file/xml-components/default-attributes.ts

@@ -24,8 +24,4 @@ export abstract class XmlAttributeComponent<T> extends BaseXmlComponent {
         });
         return { _attr: attrs };
     }
-
-    public set(properties: T): void {
-        this.root = properties;
-    }
 }