def _get_brownian_motion(self, white_noise):
    brownian_motion = np.cumsum(white_noise)
    brownian_motion = np.append(0, brownian_motion)
    return brownian_motion
def _get_brownian_motion(self, white_noise):
    brownian_motion = np.cumsum(white_noise)
    brownian_motion = np.append(0, brownian_motion)
    return brownian_motion