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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 _spline(t, p0, p1, p2, p3):
 """ Catmull-Rom cubic spline to interpolate 4 given points. :param t: Time index through the spline (must be 0-1). :param p0: The previous point in the curve (for continuity). :param p1: The first point to interpolate. :param p2: The second point to interpolate. :param p3: The last point to interpolate. """

    return (
        t * ((2 - t) * t - 1) * p0 +
        (t * t * (3 * t - 5) + 2) * p1 +
        t * ((4 - 3 * t) * t + 1) * p2 +
        (t - 1) * t * t * p3) / 2