### 12.11.3 Parabolas in space: parabola

See section 11.12.3 for parabolas in the plane.

The parabola command takes three non-collinear points as
arguments. The first point is the focus, the second point is the
vertex, and the third point determines the plane.

parabola returns and draws the corresponding parabola.

Input:

parabola(point(0,0,0),point(-1,0,0),point(1,1,1))

Output: