How to get Sender's ApiKey via API

Hi, I need to get newly created sender's API key and store it in local database. Sender class does not contain attribute APIkey. Is this even possible? How? The code i'm using is below. ..... Address address = new Address(); address.Address1 = "ln 1"; address.City = "Toronto"; address.Country = "Can"; AccountMember member = AccountMemberBuilder.NewAccountMember(email) .WithFirstName("fname") .WithLastName("last name") .WithAddress(address) .WithCompany("Brokerage name from DB") .WithPhoneNumber("123 1232 2131") .WithTitle("Mr/Ms") .WithStatus(SenderStatus.ACTIVE).Build(); Sender sender = EslClient.AccountService.InviteUser(member); ..... //at this point I'd like to return sender.ApiKey