This includes a dataframe that represents a Footprint chart of the Bid vs Ask type. Footprint charts are a type of candlestick chart that provides additional information, such as trade volume and order flow, in addition to price.
The scale of the price is set by `orderflow.scale` (see above) and thus binned per price level.
Following columns are available:
```python
orderflow_df['bid_amount'] # how much bids were traded
orderflow_df['ask_amount'] # how much asks were traded