@Override
  public PsiReference @NotNull [] getReferencesByElement(@NotNull PsiElement element, @NotNull ProcessingContext context) {
    final XmlAttributeValue value = (XmlAttributeValue)element;

    final String s = value.getValue();
    final int i = s.indexOf(':');
    if (i <= 0 || s.startsWith("xml:")) {
      return PsiReference.EMPTY_ARRAY;
    }

    return new PsiReference[]{
            new PrefixReference(value, i)
    };
  }
@Override
  public PsiReference @NotNull [] getReferencesByElement(@NotNull PsiElement element, @NotNull ProcessingContext context)