code: public void clearNamespaces( String elementName ) {
        if( StringUtils.isBlank( elementName ) ){
           rootNamespace.clear();
        }else{
           namespacesPerElement.remove( elementName );
        }
     }
docs: Removes all namespace declarations from an element.<br>
  If the elementName param is null or blank, the declarations will be
  removed from the root element.
  
  @param elementName name of target element