Retrieve the list of allowed approver email addresses.

def retrieve_approver_email_list(self, domain, product_id):
        """Retrieve the list of allowed approver email addresses."""

        response = self.request(E.retrieveApproverEmailListSslCertRequest(
            E.domain(domain),
            E.productId(product_id)
        ))

        return [str(i) for i in response.data.array[0].item]