code: public TemplateDocumentsResult updateDocuments(String accountId, String templateId, EnvelopeDefinition envelopeDefinition) throws ApiException {
      return updateDocuments(accountId, templateId, envelopeDefinition, null);
    }
docs: Adds documents to a template document.
  Adds one or more documents to an existing template document.
  @param accountId The external account number (int) or account ID Guid. (required)
  @param templateId The ID of the template being accessed. (required)
  @param envelopeDefinition  (optional)
  @return TemplateDocumentsResult