def display_format
      value = self.format_str ||
        I18n.t(self.format, :scope => [:bento_search, :format], :default => self.format.to_s.titleize)

      return value.blank? ? nil : value
    end
def display_format
      value = self.format_str ||
        I18n.t(self.format, :scope => [:bento_search, :format], :default => self.format.to_s.titleize)

      return value.blank? ? nil : value
    end
format string to display to user. Uses #format_str if present,
 otherwise finds an i18n label from #format. Returns nil if none
 available.