def content_charset
      content_types.each do |value|
        if value.include?(';')
          value.split(';').each do |param|
            param.strip!

            if param.start_with?('charset=')
              return param.split('=',2).last
            end
          end
        end
      end

      return nil
    end
def content_charset
      content_types.each do |value|
        if value.include?(';')
          value.split(';').each do |param|
            param.strip!

            if param.start_with?('charset=')
              return param.split('=',2).last
            end
          end
        end
      end

      return nil
    end
The charset included in the Content-Type.

 @return [String, nil]
   The charset of the content.

 @since 0.4.0