PayPal\Api\Billing::getBillingAgreementId PHP Method

    public function getBillingAgreementId()
    {
        return $this->billing_agreement_id;
    }

 /**
  * @depends testSerializationDeserialization
  * @param Billing $obj
  */
 public function testGetters($obj)
 {
     $this->assertEquals($obj->getBillingAgreementId(), "TestSample");
 }