def _add_amount(self,

                    currency_map: MutableMapping[str, data.Amount],

                    amount: data.Amount,

    ) -> None:

        code = amount.currency

        try:

            current_number = currency_map[code].number

        except KeyError:

            current_number = Decimal(0)

        currency_map[code] = data.Amount(current_number + amount.number, code)

    def _add_other(self,

                   currency_map: MutableMapping[str, data.Amount],

                   other: Union[data.Amount, 'Balance'],

    ) -> None:

        if isinstance(other, Balance):

            for amount in other.values():

                self._add_amount(currency_map, amount)

        else:

            self._add_amount(currency_map, other)

    def __repr__(self) -> str:

        values = [repr(amt) for amt in self.values()]

        return f"{type(self).__name__}({values!r})"

    def __str__(self) -> str:

        return self.format()

    def __abs__(self: BalanceType) -> BalanceType:

        return type(self)(bc_amount.abs(amt) for amt in self.values())

    def __add__(self: BalanceType, other: Union[data.Amount, 'Balance']) -> BalanceType:

        retval_map = self._currency_map.copy()

        self._add_other(retval_map, other)

        return type(self)(retval_map.values())

    def __eq__(self, other: Any) -> bool:

        if (self.is_zero()

            and isinstance(other, Balance)

            and other.is_zero()):

            return True

        else:

            return super().__eq__(other)

    def __neg__(self: BalanceType) -> BalanceType:

        return type(self)(-amt for amt in self.values())

    def __getitem__(self, key: str) -> data.Amount:

        return self._currency_map[key]

    def __iter__(self) -> Iterator[str]:

        return iter(self._currency_map)

    def __len__(self) -> int:

        return len(self._currency_map)

    def _all_amounts(self,

                     op_func: Callable[[DecimalCompat, DecimalCompat], bool],

                     operand: DecimalCompat,

    ) -> bool:

        return all(op_func(amt.number, operand) for amt in self.values())

    @staticmethod

    def within_tolerance(dec: DecimalCompat, tolerance: DecimalCompat) -> bool:

        dec = cast(Decimal, dec)

        return abs(dec) < tolerance

    def eq_zero(self) -> bool:

        """Returns true if all amounts in the balance == 0, within tolerance."""

        return self._all_amounts(self.within_tolerance, self.tolerance)

    is_zero = eq_zero

    def ge_zero(self) -> bool:

        """Returns true if all amounts in the balance >= 0, within tolerance."""

        op_func = operator.gt if self.tolerance else operator.ge

        return self._all_amounts(op_func, -self.tolerance)

    def le_zero(self) -> bool:

        """Returns true if all amounts in the balance <= 0, within tolerance."""

        op_func = operator.lt if self.tolerance else operator.le

        return self._all_amounts(op_func, self.tolerance)

    def format(self,

               fmt: Optional[str]='#,#00.00 ¤¤',

               sep: str=', ',

               empty: str="Zero balance",

    ) -> str:

        """Formats the balance as a string with the given parameters

        If the balance is zero, returns ``empty``. Otherwise, returns a string

        with each amount in the balance formatted as ``fmt``, separated by

        ``sep``.

        If you set ``fmt`` to None, amounts will be formatted according to the

    ({}, True),

    ({'USD': 0}, True),

    ({'USD': 0, 'EUR': 0}, True),

    ({'EUR': -10}, True),

    ({'USD': 10, 'EUR': -20}, False),

    ({'USD': -10, 'EUR': -20}, True),

    ({'JPY': 10}, False),

    ({'JPY': 10, 'BRL': 0}, False),

    ({'JPY': 10, 'BRL': 20}, False),

    ({'USD': '0.00015'}, True),

    ({'EUR': '-0.00052'}, True),

    ({'RUB': core.Balance.TOLERANCE}, False),

    ({'RUB': -core.Balance.TOLERANCE}, True),

])

def test_le_zero(mapping, expected):

    balance = core.Balance(amounts_from_map(mapping))

    assert balance.le_zero() == expected

@pytest.mark.parametrize('mapping', [

    {},

    {'USD': 0},

    {'EUR': 10},

    {'JPY': 20, 'BRL': 30},

    {'EUR': -15},

    {'JPY': -25, 'BRL': -35},

    {'JPY': 40, 'USD': 0, 'EUR': -50},

])

def test_abs(mapping):

    actual = abs(core.Balance(amounts_from_map(mapping)))

    assert set(actual) == set(mapping)

    for key, number in mapping.items():

        assert actual[key] == testutil.Amount(abs(number), key)

@pytest.mark.parametrize('mapping', [

    {},

    {'USD': 0},

    {'EUR': 10},

    {'JPY': 20, 'BRL': 30},

    {'EUR': -15},

    {'JPY': -25, 'BRL': -35},

    {'JPY': 40, 'USD': 0, 'EUR': -50},

])

def test_neg(mapping):

    actual = -core.Balance(amounts_from_map(mapping))

    assert set(actual) == set(mapping)

    for key, number in mapping.items():

        assert actual[key] == testutil.Amount(-number, key)

@pytest.mark.parametrize('map1,map2,expected', [

    ({}, {}, True),

    ({}, {'USD': 0}, True),

    ({}, {'EUR': 1}, False),

    ({'USD': 1}, {'EUR': 1}, False),

    ({'USD': 1}, {'USD': '1.0'}, True),

    ({'USD': 1}, {'USD': '1.0', 'EUR': '2.0'}, False),

    ({'USD': 1, 'BRL': '2.0'}, {'USD': '1.0', 'EUR': '2.0'}, False),

    ({'USD': 1, 'EUR': 2, 'BRL': '3.0'}, {'USD': '1.0', 'EUR': '2.0'}, False),

    ({'USD': 1, 'EUR': 2}, {'USD': '1.0', 'EUR': '2.0'}, True),

])

def test_eq(map1, map2, expected):

    bal1 = core.Balance(amounts_from_map(map1))

    bal2 = core.Balance(amounts_from_map(map2))

    actual = bal1 == bal2

    assert actual == expected

@pytest.mark.parametrize('number,currency', {

    (50, 'USD'),

    (-50, 'USD'),

    (50000, 'BRL'),

    (-4000, 'BRL'),

})

def test_add_amount(number, currency):

    start_amount = testutil.Amount(500, 'USD')

    start_bal = core.Balance([start_amount])

    add_amount = testutil.Amount(number, currency)

    actual = start_bal + add_amount

    if currency == 'USD':

        assert len(actual) == 1

        assert actual['USD'] == testutil.Amount(500 + number)

    else:

        assert len(actual) == 2

        assert actual['USD'] == start_amount

        assert actual[currency] == add_amount

    assert start_bal == {'USD': start_amount}

@pytest.mark.parametrize('number,currency', {

    (50, 'USD'),

    (-50, 'USD'),

    (50000, 'BRL'),

    (-4000, 'BRL'),

})

def test_iadd_amount(number, currency):

    balance = core.MutableBalance([testutil.Amount(500, 'USD')])

    add_amount = testutil.Amount(number, currency)

    balance += add_amount

    if currency == 'USD':