public Builder sourceIs(Source... source){
  verifyNotNull(source);
  expressions.add(new EventFilterExpression.SourceIs(source));
  return this;
}

public Builder sourceIs ( Source ... source ) { verifyNotNull ( source ) ; expressions . add ( new EventFilterExpression . SourceIs ( source ) ) ; return this ; }
add a filter for all source sections that reference one of the given sources .
