def METHOD_NAME(self, package=None):
    """Return an 'account'.
    By default, the first account encoutered for this type.
    Depending on your case, you may store it on the picking or
    compute it from your business rules.
    Accounts are resolved at runtime (can be != for dev/prod)
    """
    self.ensure_one()
    account = self._get_carrier_account()
    if not account:
        raise UserError(
            _(
                "No account available with name '%s' "
                "for this carrier" % self.carrier_id.delivery_type
            )
        )
    return account