* Currently all colours are included in legend when user passes a predicate to `trace_position` and modifies `background_color` * Could update this to exclude colours that are no longer shown on the plot * Could add a new entry to legend for the `background_color`, the name of this entry could be the expression passed to `trace_position`
trace_positionand modifiesbackground_colorbackground_color, the name of this entry could be the expression passed totrace_position