code: public static void addExpressionToAnnotationMember(AnnotationNode annotationNode, String memberName, Expression expression) {
          Expression exclude = annotationNode.getMember(memberName);
          if(exclude instanceof ListExpression) {
              ((ListExpression)exclude).addExpression(expression);
          }
          else if(exclude != null) {
              ListExpression list = new ListExpression();
              list.addExpression(exclude);
              list.addExpression(expression);
              annotationNode.setMember(memberName, list);
          }
          else {
              annotationNode.setMember(memberName, expression);
          }
      }
docs: Adds the given expression as a member of the given annotation
  
  @param annotationNode The annotation node
  @param memberName The name of the member
  @param expression The expression