# Buggy code
def trailing_space() -> List[Dimension]:
    """
    Create a trailing stoploss space.

    You may override it in your custom Hyperopt class.
    """
    return [
        # It was decided to always set trailing_stop is to True if the 'trailing' hyperspace
        # is used. Otherwise hyperopt will vary other parameters that won't have effect if
        # trailing_stop is set False.
        # This parameter is included into the hyperspace dimensions rather than assigning
        # it explicitly in the code in order to have it printed in the results along with
        # other 'trailing' hyperspace parameters.
        Categorical([True], name="trailing_stop"),
        Real(0.02, 0.35, name="trailing_stop_positive"),
        Real(0.01, 0.1, name="trailing_stop_positive_offset"),
        Categorical([True, False], name="trailing_only_offset_is_reached"),
    ]


# 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 trailing_space() -> List[Dimension]:
    """
    Create a trailing stoploss space.

    You may override it in your custom Hyperopt class.
    """
    return [
        # It was decided to always set trailing_stop is to True if the 'trailing' hyperspace
        # is used. Otherwise hyperopt will vary other parameters that won't have effect if
        # trailing_stop is set False.
        # This parameter is included into the hyperspace dimensions rather than assigning
        # it explicitly in the code in order to have it printed in the results along with
        # other 'trailing' hyperspace parameters.
        Categorical([True], name="trailing_stop"),
        Real(0.01, 0.35, name="trailing_stop_positive"),
        # 'trailing_stop_positive_offset' should be greater than 'trailing_stop_positive',
        # so this intermediate parameter is used as the value of the difference between
        # them. The value of the 'trailing_stop_positive_offset' is constructed in the
        # generate_trailing_params() method.
        # This is similar to the hyperspace dimensions used for constructing the ROI tables.
        Real(0.001, 0.1, name="trailing_stop_positive_offset_p1"),
        Categorical([True, False], name="trailing_only_offset_is_reached"),
    ]