public static @Nullable PsiClass getTagClass(@Nullable XmlTag xmlTag) {
    if (xmlTag != null) {
      final XmlElementDescriptor descriptor = xmlTag.getDescriptor();
      if (descriptor != null) {
        final PsiElement declaration = descriptor.getDeclaration();
        if (declaration instanceof PsiClass) {
          return (PsiClass)declaration;
        }
      }
    }
    return null;
  }
public static @Nullable PsiClass getTagClass(@Nullable XmlTag xmlTag)