@type t() :: %DocuSign.Model.BillingInvoice{
  amount: String.t() | nil,
  balance: String.t() | nil,
  dueDate: String.t() | nil,
  invoiceId: String.t() | nil,
  invoiceItems: [DocuSign.Model.BillingInvoiceItem.t()] | nil,
  invoiceNumber: String.t() | nil,
  invoiceUri: String.t() | nil,
  nonTaxableAmount: String.t() | nil,
  pdfAvailable: String.t() | nil,
  taxableAmount: String.t() | nil
}