def uniq(&block)
      if block
        new(attributes.uniq(&block))
      else
        new(attributes.uniq(&:name))
      end
    end
def uniq(&block)
      if block
        new(attributes.uniq(&block))
      else
        new(attributes.uniq(&:name))
      end
    end
Return a new schema with uniq attributes

 @return [Schema]

 @api public