def to_xml_string(str = '')
      serialized_tag('headerFooter', str) do
        serialized_element_attributes(str) do |value|
          value = ::CGI.escapeHTML(value)
        end
      end
    end
def to_xml_string(str = '')
      serialized_tag('headerFooter', str) do
        serialized_element_attributes(str) do |value|
          value = ::CGI.escapeHTML(value)
        end
      end
    end
Serializes the header/footer object.
 @param [String] str
 @return [String]