# File lib/net/http_multipart_post.rb, line 67
      def encode_multipart_post_files
        return "" if multipart_post_files.empty?
        if multipart_post_files.size == 1
          name = multipart_post_files.keys.first
          file = multipart_post_files.values.first
          encode_multipart_post_file(name, file)
        else
          raise "Currently more than 1 file upload is not supported."
        end
      end