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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def reverse_velocity_kalman_model():
    '''Return a KalmanState set up to model going backwards in time'''
    om = np.array([[1,0,0,0], [0, 1, 0, 0]])
    tm = np.array([[1,0,-1,0],
                   [0,1,0,-1],
                   [0,0,1,0],
                   [0,0,0,1]])
    return KalmanState(om, tm)