@Nullable
  @Override
  public MyHost collectInformation(@NotNull PsiFile file) {
    if (!(file instanceof XmlFile)) return null;
    final XmlDocument document = ((XmlFile)file).getDocument();
    if (document == null) return null;
    XmlTag rootTag = document.getRootTag();
    XmlNSDescriptor nsDescriptor = rootTag == null ? null : rootTag.getNSDescriptor(rootTag.getNamespace(), false);

    if (nsDescriptor instanceof Validator) {
      MyHost host = new MyHost();
      ((Validator<XmlDocument>)nsDescriptor).validate(document, host);
      return host;
    }
    return null;
  }
@Nullable
  @Override
  public MyHost collectInformation(@NotNull PsiFile file)