Code folding not working

Hi everyone,

I would like to fold an annotation that spans multiple lines. I extended FoldingBuilderEx, and registered my class in plugins.xml. Here is my code:

public class AnnotationFolderBuilder extends FoldingBuilderEx {
    static final private List<String> COCONUT_ANNOTATIONS = Arrays.asList(
            "@LocationAnnotation",
            "@NetworkAnnotation"
    );

    private FoldingGroup group = FoldingGroup.newGroup("annotationFoldGroup");

    @NotNull
    @Override
    public FoldingDescriptor[] buildFoldRegions(@NotNull PsiElement root, @NotNull Document document, boolean quick) {
        List<FoldingDescriptor> descriptors = new ArrayList<FoldingDescriptor>();
        Collection<PsiAnnotation> annotations =
                PsiTreeUtil.findChildrenOfType(root, PsiAnnotation.class);

        for(final PsiAnnotation annotation : annotations) {
            if(isCoconutAnnotation(annotation.getText())) {
                descriptors.add(createFoldingDescriptor(annotation));
            }
        }

        return descriptors.toArray(new FoldingDescriptor[descriptors.size()]);
    }

    private boolean isCoconutAnnotation(String annotationText) {
        for(final String annotation : COCONUT_ANNOTATIONS) {
            if(annotationText.contains(annotation)) {
                return true;
            }
        }

        return false;
    }

    private FoldingDescriptor createFoldingDescriptor(PsiAnnotation annotation) {
        System.out.println(annotation.getText() + " has range " +
                annotation.getTextRange().getStartOffset() + " - " +
                annotation.getTextRange().getEndOffset());
        return new FoldingDescriptor(annotation.getNode(),
                new TextRange(annotation.getTextRange().getStartOffset() + 4,
                              annotation.getTextRange().getEndOffset() - 1),
                group) {
            @Nullable
            @Override
            public String getPlaceholderText() {
                // IMPORTANT: keys can come with no values, so a test for null is needed
                // IMPORTANT: Convert embedded \n to backslash n, so that the string will look like it has LF embedded
                // in it and embedded " to escaped "
                return "\\n".replaceAll("\"", "\\\\\"");
            }
        };
    }

    @Nullable
    @Override
    public String getPlaceholderText(@NotNull ASTNode node) {
        return "...";
    }

    @Override
    public boolean isCollapsedByDefault(@NotNull ASTNode node) {
        return true;
    }
}

The annotation is not folding or doing anything in the test program. Any help or further explanation of how FoldingBuilders work would be great (ex: why are there two getPlaceHolderTexts?)

Thanks!