def calculate_means(x_s, y_s):
    """
        Calculate mean of each total timestep and average episodic return over all
        trials at each iteration.

        Parameters:
            x_s - A list of lists of total timesteps so far per seed.
            y_s - A list of lists of average episodic return per seed

        Return: 
            Means of x_s and y_s 
    """
    if len(x_s) == 1:
        return x_s, y_s

    return list(np.mean(x_s, axis=0)), list(np.mean(y_s, axis=0))
Calculate mean of each total timestep and average episodic return over all
trials at each iteration.

Parameters:
x_s - A list of lists of total timesteps so far per seed.
y_s - A list of lists of average episodic return per seed

Return:
Means of x_s and y_s
part4/make_graph.py