def sign(tx_template)
      return tx_template if @xpubs_by_signer.empty?

      @xpubs_by_signer.each do |signer_conn, xpubs|
        tx_template = signer_conn.singleton_batch_request(
          '/sign-transaction',
          transactions: [tx_template],
          xpubs: xpubs,
        ) { |item| Transaction::Template.new(item) }
      end

      tx_template
    end
def sign(tx_template)
      return tx_template if @xpubs_by_signer.empty?

      @xpubs_by_signer.each do |signer_conn, xpubs|
        tx_template = signer_conn.singleton_batch_request(
          '/sign-transaction',
          transactions: [tx_template],
          xpubs: xpubs,
        ) { |item| Transaction::Template.new(item) }
      end

      tx_template
    end
Sign a single transaction
 @param [Hash] tx_template	A single transaction template.