def clean_value
      if (type == :string || type == :text) && !Axlsx::trust_input
        Axlsx::sanitize(::CGI.escapeHTML(@value.to_s))
      else
        @value.to_s
      end
    end
def clean_value
      if (type == :string || type == :text) && !Axlsx::trust_input
        Axlsx::sanitize(::CGI.escapeHTML(@value.to_s))
      else
        @value.to_s
      end
    end
Returns the sanatized value
 TODO find a better way to do this as it accounts for 30% of
 processing time in benchmarking...