# Buggy code
def get_trade_stake_amount(self, pair) -> float:
    """
    Calculate stake amount for the trade
    :return: float: Stake amount
    :raise: DependencyException if the available stake amount is too low
    """
    stake_amount: float
    # Ensure wallets are uptodate.
    self.wallets.update()

    if self.edge:
        stake_amount = 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"]
        if stake_amount == constants.UNLIMITED_STAKE_AMOUNT:
            stake_amount = self._calculate_unlimited_stake_amount()

    return self._check_available_stake_amount(stake_amount)


# Traceback (Exception)
2020-02-20 22:47:28,025 - freqtrade - ERROR - Fatal exception!
Traceback (most recent call last):
File "/opt/tradebot/freqtrade/.env/lib/python3.7/site-packages/talib/__init__.py", line 20, in wrapper
for arg in chain(args, kwargs.values())
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/freqtrade/freqtrade/main.py", line 36, in main
return_code = args['func'](args)
File "/freqtrade/freqtrade/commands/optimize_commands.py", line 76, in start_hyperopt
hyperopt.start()
File "/freqtrade/freqtrade/optimize/hyperopt.py", line 488, in start
preprocessed = self.backtesting.strategy.tickerdata_to_dataframe(data)
File "/freqtrade/freqtrade/strategy/interface.py", line 448, in tickerdata_to_dataframe
for pair, pair_data in tickerdata.items()}
File "/freqtrade/freqtrade/strategy/interface.py", line 448, in <dictcomp>
for pair, pair_data in tickerdata.items()}
File "/freqtrade/freqtrade/strategy/interface.py", line 464, in advise_indicators
return self.populate_indicators(dataframe, metadata)
File "/freqtrade/user_data/strategies/MyDev.py", line 205, in populate_indicators
dataframe['mfi'] = ta.MFI(dataframe)
File "talib/_abstract.pxi", line 352, in talib._ta_lib.Function.__call__
File "talib/_abstract.pxi", line 383, in talib._ta_lib.Function.__call_function
File "/opt/tradebot/freqtrade/.env/lib/python3.7/site-packages/talib/__init__.py", line 24, in wrapper
return func(*args, **kwargs)
File "talib/_func.pxi", line 8454, in talib._ta_lib.MFI
Exception: volume is not double

# Fixed code
def get_trade_stake_amount(self, pair: str) -> float:
    """
    Calculate stake amount for the trade
    :return: float: Stake amount
    :raise: DependencyException if the available stake amount is too low
    """
    stake_amount: float
    # Ensure wallets are uptodate.
    self.wallets.update()

    if self.edge:
        stake_amount = 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"]
        if stake_amount == constants.UNLIMITED_STAKE_AMOUNT:
            stake_amount = self._calculate_unlimited_stake_amount()

    return self._check_available_stake_amount(stake_amount)