def vault_billing_address
      return nil if billing_details.id.nil?
      @gateway.address.find(customer_details.id, billing_details.id)
    end
def vault_billing_address
      return nil if billing_details.id.nil?
      @gateway.address.find(customer_details.id, billing_details.id)
    end
If this transaction was stored in the vault, or created from vault records,
 vault_billing_address will return the associated Braintree::Address. Because the
 vault billing address can be updated after the transaction was created, the attributes
 on vault_billing_address may not match the attributes on billing_details.