@NotNull
  String getNamespace() {
    final String name = myAttribute.getName();
    final String prefixByQualifiedName = XmlUtil.findPrefixByQualifiedName(name);
    // The namespace name for an unprefixed attribute name always has no value. Namespace recommendation section 6.2, third paragraph
    if (prefixByQualifiedName.isEmpty()) return XmlUtil.EMPTY_URI;
    return myAttribute.getParent().getNamespaceByPrefix(prefixByQualifiedName);
  }
@NotNull
  String getNamespace()