def normalize_klass_for_type_name(klass)
      case klass
      when Symbol then klass
      when Array then ARRAY_KEY
      when Set then SET_KEY
      when String then underscore(klass)
      else
        underscore(klass.name)
      end
    end
def normalize_klass_for_type_name(klass)
      case klass
      when Symbol then klass
      when Array then ARRAY_KEY
      when Set then SET_KEY
      when String then underscore(klass)
      else
        underscore(klass.name)
      end
    end
DateTime => :date_time