How to use the chempy.cpv.add function in chempy

v1_t = cpv.normalize(cpv.sub(p1_t, p2_t))
        v2_t = cpv.normalize(cpv.sub(p3_t, p2_t))
        normal_t = cpv.normalize(cpv.cross_product(v1_t, v2_t))
        v2_t = cpv.normalize(cpv.cross_product(normal_t, v1_t))
        p1_t2 = cpv.add(v1_t, p2_t)
        p3_t2 = cpv.add(v2_t, p2_t)
        print_info("Newnormal", p1_t2, p2_t, p3_t2)

    if vm1!=None:
        v1 = cpv.scale(cpv.normalize(v1), vm1)
    if vm2!=None:
        v2 = cpv.scale(cpv.normalize(v2), vm2)

    centrum = p2
    if center:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.sub(cpv.add(centrum, v1), v2)
        corner3 = cpv.sub(cpv.sub(centrum, v1), v2)
        corner4 = cpv.add(cpv.sub(centrum, v1), v2)
    else:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.add(centrum, v1)
        corner3 = centrum
        corner4 = cpv.add(centrum, v2)

    return plane(corner1, corner2, corner3, corner4, normal, settings)

v1_t = cpv.normalize(cpv.sub(p1_t, p2_t))
        v2_t = cpv.normalize(cpv.sub(p3_t, p2_t))
        normal_t = cpv.normalize(cpv.cross_product(v1_t, v2_t))
        v2_t = cpv.normalize(cpv.cross_product(normal_t, v1_t))
        p1_t2 = cpv.add(v1_t, p2_t)
        p3_t2 = cpv.add(v2_t, p2_t)
        print_info("Newnormal", p1_t2, p2_t, p3_t2)

    if vm1!=None:
        v1 = cpv.scale(cpv.normalize(v1), vm1)
    if vm2!=None:
        v2 = cpv.scale(cpv.normalize(v2), vm2)

    centrum = p2
    if center:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.sub(cpv.add(centrum, v1), v2)
        corner3 = cpv.sub(cpv.sub(centrum, v1), v2)
        corner4 = cpv.add(cpv.sub(centrum, v1), v2)
    else:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.add(centrum, v1)
        corner3 = centrum
        corner4 = cpv.add(centrum, v2)

    return plane(corner1, corner2, corner3, corner4, normal, settings)

def cgo_tetrahedron(x, y, z, r):
    vertices = [cpv.add((x, y, z), cpv.scale(v, r)) for v in [
        [0., 1., 0.],
        [0.0, -0.3338068592337708, 0.9426414910921784],
        [0.8163514779470693, -0.3338068592337708, -0.471320745546089],
        [-0.816351477947069, -0.3338068592337708, -0.4713207455460897]
    ]]
    return [
        cgo.BEGIN, cgo.TRIANGLES,
        cgo.NORMAL, 0.8165448970931916, 0.33317549135767066, 0.4714324161421696,
        cgo.VERTEX] + vertices[0] + [
        cgo.VERTEX] + vertices[1] + [
        cgo.VERTEX] + vertices[2] + [
        cgo.NORMAL, 0., 0.3331754913576707, -0.9428648322843389,
        cgo.VERTEX] + vertices[0] + [
        cgo.VERTEX] + vertices[2] + [
        cgo.VERTEX] + vertices[3] + [
        cgo.NORMAL, -0.8165448970931919, 0.3331754913576705, 0.4714324161421693,

if vm1!=None:
        v1 = cpv.scale(cpv.normalize(v1), vm1)
    if vm2!=None:
        v2 = cpv.scale(cpv.normalize(v2), vm2)

    centrum = p2
    if center:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.sub(cpv.add(centrum, v1), v2)
        corner3 = cpv.sub(cpv.sub(centrum, v1), v2)
        corner4 = cpv.add(cpv.sub(centrum, v1), v2)
    else:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.add(centrum, v1)
        corner3 = centrum
        corner4 = cpv.add(centrum, v2)

    return plane(corner1, corner2, corner3, corner4, normal, settings)

v2 = cpv.sub(p3, p2)
    normal = cpv.cross_product(v1, v2)

    if 'translate' in settings:
        vtran = cpv.scale(cpv.normalize(normal), settings['translate'])
        p1_t = cpv.sub(p1, vtran)
        p2_t = cpv.sub(p2, vtran)
        p3_t = cpv.sub(p3, vtran)
        print("New coordinates are:")
        print_info("New", p1_t, p2_t, p3_t)
        print("New coordinates are for normalized plane:")
        v1_t = cpv.normalize(cpv.sub(p1_t, p2_t))
        v2_t = cpv.normalize(cpv.sub(p3_t, p2_t))
        normal_t = cpv.normalize(cpv.cross_product(v1_t, v2_t))
        v2_t = cpv.normalize(cpv.cross_product(normal_t, v1_t))
        p1_t2 = cpv.add(v1_t, p2_t)
        p3_t2 = cpv.add(v2_t, p2_t)
        print_info("Newnormal", p1_t2, p2_t, p3_t2)

    if vm1!=None:
        v1 = cpv.scale(cpv.normalize(v1), vm1)
    if vm2!=None:
        v2 = cpv.scale(cpv.normalize(v2), vm2)

    centrum = p2
    if center:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)
        corner2 = cpv.sub(cpv.add(centrum, v1), v2)
        corner3 = cpv.sub(cpv.sub(centrum, v1), v2)
        corner4 = cpv.add(cpv.sub(centrum, v1), v2)
    else:
        corner1 = cpv.add(cpv.add(centrum, v1), v2)

def calculateNewPoint(p1, p2, distance):
    v1 = cpv.normalize(cpv.sub(p1, p2))
    return cpv.add(p1, cpv.scale(v1, distance))

def _vec_sum(vec_list):
    # this is the same as
    # return numpy.array(vec_list).sum(0).tolist()
    vec = cpv.get_null()
    for x in vec_list:
        vec = cpv.add(vec, x)
    return vec