human
Complete this python program:
def fan_out_fan_in():
assistant
#Here is the Python code you requested.

    """The \Pearlmutter test\
    """
    def fun(x):
        for i in range((10 ** 4)):
            x = ((x + x) / 2.0)
        return np.sum(x)
    with tictoc():
        grad(fun)(1.0)