# File lib/aws/record/validator.rb, line 181
      def ensure_is value_or_values, *keys
        values = Array(value_or_values)
        keys.each do |key|
          next unless options.has_key?(key)
          unless values.include?(options[key])
            valid = values.map{|v| v.is_a?(Symbol) ? ":#{v}" : v.to_s }.join(', ')
            raise ArgumentError, "expected :#{key} to be one of #{valid}"
          end
        end
      end