attribute_of (REXML::DocType)

    # File src/rexml/doctype.rb, line 74
                    def attribute_of element, attribute
                            att_decl = find do |child|
                                    child.kind_of? AttlistDecl and
                                    child.element_name == element and
                                    child.include? attribute
                            end
                            return nil unless att_decl
                            att_decl[attribute]
                    end