def to_xml_string(str = '')
      valid = RichTextRun::INLINE_STYLES
      data = Hash[self.instance_values.map{ |k, v| [k.to_sym, v] }]
      data = data.select { |key, value| valid.include?(key) && !value.nil? }

      str << '<r><rPr>'
      data.keys.each do |key|
        case key
        when :font_name
          str << ('<rFont val="' << font_name << '"/>')
        when :color
          str << data[key].to_xml_string
        else
          str << ('<' << key.to_s << ' val="' << xml_value(data[key]) << '"/>')
        end
      end
      clean_value = Axlsx::trust_input ? @value.to_s : ::CGI.escapeHTML(Axlsx::sanitize(@value.to_s))
      str << ('</rPr><t>' << clean_value << '</t></r>')
    end
def to_xml_string(str = '')
      valid = RichTextRun::INLINE_STYLES
      data = Hash[self.instance_values.map{ |k, v| [k.to_sym, v] }]
      data = data.select { |key, value| valid.include?(key) && !value.nil? }

      str << '<r><rPr>'
      data.keys.each do |key|
        case key
        when :font_name
          str << ('<rFont val="' << font_name << '"/>')
        when :color
          str << data[key].to_xml_string
        else
          str << ('<' << key.to_s << ' val="' << xml_value(data[key]) << '"/>')
        end
      end
      clean_value = Axlsx::trust_input ? @value.to_s : ::CGI.escapeHTML(Axlsx::sanitize(@value.to_s))
      str << ('</rPr><t>' << clean_value << '</t></r>')
    end
Serializes the RichTextRun
 @param [String] str
 @return [String]