addAnnotation(i, a) {
    const u = this.splitClassNameAndType(i).className;
    this.classes.get(u).annotations.push(a);
  }
Adds an annotation to the specified class Annotations mark special properties of the given type
(like 'interface' or 'service')

@param className - The class name
@param annotation - The name of the annotation without any brackets
@public