Update show() functions to allow plotting both conf and pred simulataneously

[rwood-97]

Is your feature request related to a problem? Please describe. At the moment, you can only plot one column at a time using the show function. i.e. you can only plot the predicted labels or the confidence scores but not both at the same time. This is annoying as it would be useful to see both simulatenously.

Describe the solution you'd like Some options of how this could be improved:

1. Each label could have its own colour (same as currently happens when you call show() with "pred"). You could then set the confidence score as the alpha value for these (potentially up to a max alpha of 0.5).
2. Each label has its own colour scale, eg. https://matplotlib.org/stable/users/explain/colors/colormaps.html#sequential. but alpha stays constant.
3. You plot "conf" but filter for only one label at a time. All the rest have alpha=0 (i.e. no colour).

Relates to this view.