def show_canvas(self, canvas, **kwargs):
        raise NotImplementedError
:returns: (extra_consumed, free_units)
dataset/ETHPy150Open SheffieldML/GPy/GPy/plotting/abstract_plotting_library.py/AbstractPlottingLibrary.show_canvas--crossover with--dataset/ETHPy150Open PressLabs/silver/silver/models.py/Subscription._get_extra_consumed_units_during_trial