# File lib/aws/dynamo_db/primary_key_element.rb, line 32
      def self.from_description(description)
        (name, type, *extra) = description.to_a.flatten

        raise(ArgumentError,
              "key element may contain only one name/type pair") unless
          extra.empty?

        raise ArgumentError, "unsupported type #{type.inspect}" unless
          ATTRIBUTE_TYPES.values.include?(type.to_sym)

        new(:name => name.to_s, :type => type)
      end