t() :: %AdyenCheckoutEx.Model.Mandate{
  amount: String.t(),
  amountRule: String.t() | nil,
  billingAttemptsRule: String.t() | nil,
  billingDay: String.t() | nil,
  endsAt: String.t(),
  frequency: String.t(),
  remarks: String.t() | nil,
  startsAt: String.t() | nil
}