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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 segment_volume(seg):
    '''Compute the volume of a segment.

    Approximated as a conical frustum.
    '''
    r0 = seg[0][COLS.R]
    r1 = seg[1][COLS.R]
    h = point_dist(seg[0], seg[1])
    return math.pi * h * ((r0 * r0) + (r0 * r1) + (r1 * r1)) / 3.0