# File lib/aws/s3/presigned_post.rb, line 354
      def refine(opts)
        self.class.new(bucket, {
                         :conditions => conditions,
                         :key => key,
                         :metadata => metadata,
                         :secure => secure?,
                         :content_length => content_length,
                         :expires => expires
                       }.merge(@fields).
                       merge(opts))
      end