How to use the freqtrade.constants function in freqtrade

def test_init_dryrun_db(default_conf, mocker):
    default_conf.update({'dry_run': True})
    default_conf.update({'db_url': constants.DEFAULT_DB_DRYRUN_URL})

    create_engine_mock = mocker.patch('freqtrade.persistence.create_engine', MagicMock())

    init(default_conf['db_url'], default_conf['dry_run'])
    assert create_engine_mock.call_count == 1
    assert create_engine_mock.mock_calls[0][1][0] == 'sqlite:///tradesv3.dryrun.sqlite'

def test_create_trades_limit_reached(default_conf, ticker, limit_buy_order,
                                     fee, markets, mocker) -> None:
    patch_RPCManager(mocker)
    patch_exchange(mocker)
    mocker.patch.multiple(
        'freqtrade.exchange.Exchange',
        get_ticker=ticker,
        buy=MagicMock(return_value={'id': limit_buy_order['id']}),
        get_balance=MagicMock(return_value=default_conf['stake_amount']),
        get_fee=fee,
    )
    default_conf['max_open_trades'] = 0
    default_conf['stake_amount'] = constants.UNLIMITED_STAKE_AMOUNT

    freqtrade = FreqtradeBot(default_conf)
    patch_get_signal(freqtrade)

    assert not freqtrade.create_trades()
    assert freqtrade._get_trade_stake_amount('ETH/BTC') is None

def setup_configuration(args: Namespace) -> Dict[str, Any]:
    """
    Prepare the configuration for the backtesting
    :param args: Cli args from Arguments()
    :return: Configuration
    """
    configuration = Configuration(args)
    config = configuration.get_config()

    # Ensure we do not use Exchange credentials
    config['exchange']['key'] = ''
    config['exchange']['secret'] = ''

    if config['stake_amount'] == constants.UNLIMITED_STAKE_AMOUNT:
        raise DependencyException('stake amount could not be "%s" for backtesting' %
                                  constants.UNLIMITED_STAKE_AMOUNT)

    return config

def _init(self, reconfig: bool) -> None:
        """
        Also called from the _reconfigure() method (with reconfig=True).
        """
        if reconfig or self._config is None:
            # Load configuration
            self._config = Configuration(self._args, None).get_config()

        # Init the instance of the bot
        self.freqtrade = FreqtradeBot(self._config)

        self._throttle_secs = self._config.get('internals', {}).get(
            'process_throttle_secs',
            constants.PROCESS_THROTTLE_SECS
        )

        self._sd_notify = sdnotify.SystemdNotifier() if \
            self._config.get('internals', {}).get('sd_notify', False) else None

def _parse_args(self) -> argparse.Namespace:
        """
        Parses given arguments and returns an argparse Namespace instance.
        """
        parsed_arg = self.parser.parse_args(self.args)

        # Workaround issue in argparse with action='append' and default value
        # (see https://bugs.python.org/issue16399)
        # Allow no-config for certain commands (like downloading / plotting)
        if ('config' in parsed_arg and parsed_arg.config is None and
            ((Path.cwd() / constants.DEFAULT_CONFIG).is_file() or
             not ('command' in parsed_arg and parsed_arg.command in NO_CONF_REQURIED))):
            parsed_arg.config = [constants.DEFAULT_CONFIG]

        return parsed_arg

if len(trades) == 0:
            logger.info("Applying fee on amount for %s failed: myTrade-Dict empty found", trade)
            return order_amount
        amount = 0
        fee_abs = 0
        for exectrade in trades:
            amount += exectrade['amount']
            if ("fee" in exectrade and exectrade['fee'] is not None and
                    (exectrade['fee'].keys() >= {'currency', 'cost'})):
                # only applies if fee is in quote currency!
                if (exectrade['fee']['currency'] is not None and
                        exectrade['fee']['cost'] is not None and
                        trade.pair.startswith(exectrade['fee']['currency'])):
                    fee_abs += exectrade['fee']['cost']

        if not isclose(amount, order_amount, abs_tol=constants.MATH_CLOSE_PREC):
            logger.warning(f"Amount {amount} does not match amount {trade.amount}")
            raise DependencyException("Half bought? Amounts don't match")
        real_amount = amount - fee_abs
        if fee_abs != 0:
            logger.info(f"Applying fee on amount for {trade} "
                        f"(from {order_amount} to {real_amount}) from Trades")
        return real_amount

def validate_config_schema(conf: Dict[str, Any]) -> Dict[str, Any]:
    """
    Validate the configuration follow the Config Schema
    :param conf: Config in JSON format
    :return: Returns the config if valid, otherwise throw an exception
    """
    try:
        FreqtradeValidator(constants.CONF_SCHEMA).validate(conf)
        return conf
    except ValidationError as e:
        logger.critical(
            f"Invalid configuration. See config.json.example. Reason: {e}"
        )
        raise ValidationError(
            best_match(Draft4Validator(constants.CONF_SCHEMA).iter_errors(conf)).message
        )

def setup_configuration(args: Dict[str, Any], method: RunMode) -> Dict[str, Any]:
    """
    Prepare the configuration for the Hyperopt module
    :param args: Cli args from Arguments()
    :return: Configuration
    """
    config = setup_utils_configuration(args, method)

    if method == RunMode.BACKTEST:
        if config['stake_amount'] == constants.UNLIMITED_STAKE_AMOUNT:
            raise DependencyException('stake amount could not be "%s" for backtesting' %
                                      constants.UNLIMITED_STAKE_AMOUNT)

    return config

for the stake currency
        :return: float: Stake Amount
        """
        if self.edge:
            return self.edge.stake_amount(
                pair,
                self.wallets.get_free(self.config['stake_currency']),
                self.wallets.get_total(self.config['stake_currency']),
                Trade.total_open_trades_stakes()
            )
        else:
            stake_amount = self.config['stake_amount']

        available_amount = self.wallets.get_free(self.config['stake_currency'])

        if stake_amount == constants.UNLIMITED_STAKE_AMOUNT:
            open_trades = len(Trade.get_open_trades())
            if open_trades >= self.config['max_open_trades']:
                logger.warning("Can't open a new trade: max number of trades is reached")
                return None
            return available_amount / (self.config['max_open_trades'] - open_trades)

        # Check if stake_amount is fulfilled
        if available_amount < stake_amount:
            raise DependencyException(
                f"Available balance ({available_amount} {self.config['stake_currency']}) is "
                f"lower than stake amount ({stake_amount} {self.config['stake_currency']})"
            )

        return stake_amount

def __init__(self, config: Dict[str, Any]) -> None:
        self.config = config

        # Reset keys for edge
        remove_credentials(self.config)
        self.config['stake_amount'] = constants.UNLIMITED_STAKE_AMOUNT
        self.exchange = Exchange(self.config)
        self.strategy = StrategyResolver(self.config).strategy

        validate_config_consistency(self.config)

        self.edge = Edge(config, self.exchange, self.strategy)
        # Set refresh_pairs to false for edge-cli (it must be true for edge)
        self.edge._refresh_pairs = False

        self.edge._timerange = TimeRange.parse_timerange(None if self.config.get(
            'timerange') is None else str(self.config.get('timerange')))