# Buggy code
def get_fee(
    self, symbol, type="", side="", amount=1, price=1, taker_or_maker="maker"
) -> float:
    try:
        # validate that markets are loaded before trying to get fee
        if self._api.markets is None or len(self._api.markets) == 0:
            self._api.load_markets()

        return self._api.calculate_fee(
            symbol=symbol,
            type=type,
            side=side,
            amount=amount,
            price=price,
            takerOrMaker=taker_or_maker,
        )["rate"]
    except (ccxt.NetworkError, ccxt.ExchangeError) as e:
        raise TemporaryError(
            f"Could not get fee info due to {e.__class__.__name__}. Message: {e}"
        ) from e
    except ccxt.BaseError as e:
        raise OperationalException(e) from e


# 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_fee(
    self,
    symbol: str,
    type: str = "",
    side: str = "",
    amount: float = 1,
    price: float = 1,
    taker_or_maker: str = "maker",
) -> float:
    try:
        # validate that markets are loaded before trying to get fee
        if self._api.markets is None or len(self._api.markets) == 0:
            self._api.load_markets()

        return self._api.calculate_fee(
            symbol=symbol,
            type=type,
            side=side,
            amount=amount,
            price=price,
            takerOrMaker=taker_or_maker,
        )["rate"]
    except (ccxt.NetworkError, ccxt.ExchangeError) as e:
        raise TemporaryError(
            f"Could not get fee info due to {e.__class__.__name__}. Message: {e}"
        ) from e
    except ccxt.BaseError as e:
        raise OperationalException(e) from e