private static XmlFile getRedefinedElementDescriptorFile(final XmlTag parentTag) {
    XmlAttribute attribute = parentTag.getAttribute(XmlUtil.SCHEMA_LOCATION_ATT);
    if (attribute != null) {
      XmlAttributeValue element = attribute.getValueElement();
      PsiElement psiElement = new URLReference(element).resolve();
        if (psiElement instanceof XmlFile) {
          return ((XmlFile)psiElement);
        }
    }
    return null;
  }
private static XmlFile getRedefinedElementDescriptorFile(final XmlTag parentTag)