# Buggy code
def _check_depth_of_market_buy(self, pair: str, conf: Dict) -> bool:
    """
    Checks depth of market before executing a buy
    """
    conf_bids_to_ask_delta = conf.get("bids_to_ask_delta", 0)
    logger.info("checking depth of market for %s", pair)
    order_book = self.exchange.get_order_book(pair, 1000)
    order_book_data_frame = order_book_to_dataframe(
        order_book["bids"], order_book["asks"]
    )
    order_book_bids = order_book_data_frame["b_size"].sum()
    order_book_asks = order_book_data_frame["a_size"].sum()
    bids_ask_delta = order_book_bids / order_book_asks
    logger.info(
        "bids: %s, asks: %s, delta: %s",
        order_book_bids,
        order_book_asks,
        bids_ask_delta,
    )
    if bids_ask_delta >= conf_bids_to_ask_delta:
        return True
    return False


# 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 _check_depth_of_market_buy(self, pair: str, conf: Dict) -> bool:
    """
    Checks depth of market before executing a buy
    """
    conf_bids_to_ask_delta = conf.get("bids_to_ask_delta", 0)
    logger.info(f"Checking depth of market for {pair} ...")
    order_book = self.exchange.get_order_book(pair, 1000)
    order_book_data_frame = order_book_to_dataframe(
        order_book["bids"], order_book["asks"]
    )
    order_book_bids = order_book_data_frame["b_size"].sum()
    order_book_asks = order_book_data_frame["a_size"].sum()
    bids_ask_delta = order_book_bids / order_book_asks
    logger.info(
        f"Bids: {order_book_bids}, Asks: {order_book_asks}, Delta: {bids_ask_delta}, "
        f"Bid Price: {order_book['bids'][0][0]}, Ask Price: {order_book['asks'][0][0]}, "
        f"Immediate Bid Quantity: {order_book['bids'][0][1]}, "
        f"Immediate Ask Quantity: {order_book['asks'][0][1]}."
    )
    if bids_ask_delta >= conf_bids_to_ask_delta:
        logger.info(f"Bids to asks delta for {pair} DOES satisfy condition.")
        return True
    else:
        logger.info(f"Bids to asks delta for {pair} does not satisfy condition.")
        return False