add_subplot mplfinance

 https://stackoverflow.com/questions/3584805/in-matplotlib-what-does-the-argument-mean-in-fig-add-subplot111

3

The add_subplot() method has several call signatures:

1. add_subplot(nrows, ncols, index, **kwargs)
2. add_subplot(pos, **kwargs)
3. add_subplot(ax)
4. add_subplot() <-- since 3.1