add_namespace (REXML::Element)

    # File temp/element.rb, line 250
                    def add_namespace( prefix, uri=nil )
                            unless uri
                                    @attributes["xmlns"] = prefix
                            else
                                    prefix = "xmlns:#{prefix}" unless prefix =~ /^xmlns:/
                                    @attributes[ prefix ] = uri
                            end
                            self
                    end