Plots a histogram of the results after the Monte Carlo simulation is
        run. NOTE- This method must be called AFTER "roll_mc".

        :param title_prefix: If desired, prefix the title (such as "Alg 1")
        :param title_override: Override the title string entirely
        :param figsize: The size of the histogram plot
        :return: a seaborn figure of the histogram

def plot_histogram(self, title_prefix="", title_override="",
                       figsize=(8, 6)):
        """
        Plots a histogram of the results after the Monte Carlo simulation is
        run. NOTE- This method must be called AFTER "roll_mc".

        :param title_prefix: If desired, prefix the title (such as "Alg 1")
        :param title_override: Override the title string entirely
        :param figsize: The size of the histogram plot
        :return: a seaborn figure of the histogram
        """
        # Check that roll_mc has been called
        if not self.arr_res:
            raise ValueError("Call roll_mc before plotting the histogram.")
        # Find a title using either the override or _construct_title method
        if title_override:
            title = title_override
        else:
            title = title_prefix + PBE._construct_title(self.num_dice,
                self.dice_type, self.add_val, self.num_attribute,
                self.keep_attribute, self.keep_dice, self.reroll,
                self.num_arrays)
        # Construct the histogram
        f = self._plot_hist(self.arr_res, self.pbe_res, title, figsize)
        return f