@Override
  public PsiElement copy() {
    HashMap<String, CachedValue<XmlNSDescriptor>> cacheStrict = new HashMap<>(
      myDefaultDescriptorsCacheStrict
    );
    HashMap<String, CachedValue<XmlNSDescriptor>> cacheNotStrict = new HashMap<>(
      myDefaultDescriptorsCacheNotStrict
    );
    final XmlDocumentImpl copy = (XmlDocumentImpl)super.copy();
    updateSelfDependentDtdDescriptors(copy, cacheStrict, cacheNotStrict);
    return copy;
  }
@Override
  public PsiElement copy()