# Buggy code
def trades_to_ohlcv(trades: list, timeframe: str) -> list:
    """
    Converts trades list to ohlcv list
    :param trades: List of trades, as returned by ccxt.fetch_trades.
    :param timeframe: Ticker timeframe to resample data to
    :return: ohlcv timeframe as list (as returned by ccxt.fetch_ohlcv)
    """
    from freqtrade.exchange import timeframe_to_minutes

    ticker_minutes = timeframe_to_minutes(timeframe)
    df = pd.DataFrame(trades)
    df["datetime"] = pd.to_datetime(df["datetime"])
    df = df.set_index("datetime")

    df_new = df["price"].resample(f"{ticker_minutes}min").ohlc()
    df_new["volume"] = df["amount"].resample(f"{ticker_minutes}min").sum()
    df_new["date"] = df_new.index.astype("int64") // 10**6
    # Drop 0 volume rows
    df_new = df_new.dropna()
    columns = ["date", "open", "high", "low", "close", "volume"]
    return list(zip(*[df_new[x].values.tolist() for x in columns]))


# 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 trades_to_ohlcv(trades: list, timeframe: str) -> DataFrame:
    """
    Converts trades list to ohlcv list
    TODO: This should get a dedicated test
    :param trades: List of trades, as returned by ccxt.fetch_trades.
    :param timeframe: Ticker timeframe to resample data to
    :return: ohlcv Dataframe.
    """
    from freqtrade.exchange import timeframe_to_minutes

    ticker_minutes = timeframe_to_minutes(timeframe)
    df = pd.DataFrame(trades)
    df["datetime"] = pd.to_datetime(df["datetime"])
    df = df.set_index("datetime")

    df_new = df["price"].resample(f"{ticker_minutes}min").ohlc()
    df_new["volume"] = df["amount"].resample(f"{ticker_minutes}min").sum()
    df_new["date"] = df_new.index
    # Drop 0 volume rows
    df_new = df_new.dropna()
    return df_new[DEFAULT_DATAFRAME_COLUMNS]