Octant finder

You will write three small functions about the octants and the axes. The checker uses points in all eight octants and points on planes and axes.

The idea. The signs of the three coordinates decide the octant. Octants 1 to 4 lie above the $xy$-plane and follow the quadrants of $(x, y)$. Octants 5 to 8 lie below.

Your tasks.

1. Finish octant(x, y, z). Return the octant number from 1 to 8, or 0 if any coordinate is zero.
2. Finish count_in_octant(points, n). Count how many points of the list are in octant n.
3. Finish on_axis(x, y, z). Return True if the point lies on an axis, which means that at least two coordinates are zero.