public String getPrefixByNamespace(String namespace) {
final PsiElement parent = getParent();
BidirectionalMap<String, String> map = initNamespaceMaps(parent);
if (map != null) {
List<String> keysByValue = map.getKeysByValue(namespace);
final String ns = keysByValue == null || keysByValue.isEmpty() ? null : keysByValue.get(0);
if (ns != null) return ns;
}
if (parent instanceof XmlTag) return ((XmlTag) parent).getPrefixByNamespace(namespace);
// The prefix 'xml' is by definition bound to the namespace name
// http://www.w3.org/XML/1998/namespace. It MAY, but need not, be declared
if (XmlUtil.XML_NAMESPACE_URI.equals(namespace)) return XML_NS_PREFIX;
return null;
}
