def fee
      response = JSON.parse(@client.get("transactions/#{send(:id)}/fees").body)
      response.key?('fees') ? Promisepay::Fee.new(@client, response['fees']) : nil
    end
def fee
      response = JSON.parse(@client.get("transactions/#{send(:id)}/fees").body)
      response.key?('fees') ? Promisepay::Fee.new(@client, response['fees']) : nil
    end
Gets a transactions fee details if applicable.

 @see https://reference.promisepay.com/#shows-transaction-fees

 @return [Promisepay::Fee]