Checking whether an object in space is a rhombus

See Section 26.15.9 for checking for rhombuses in 2D geometry.

The is_rhombus command determines whether or not a geometric object is a rhombus.

is_rhombus takes G, a geometric object or a sequence of four points assumed to be the vertices of a quadrilateral.
is_square(G) returns 1 if G is a rhombus but not a square, returns 2 if G is a square and returns 0 otherwise.

is_rhombus([2,0,0],[0,1,0],[-2,0,0],[0,-1,0])

R:=rhombus([0,0,0],[2,0,0],[[0,0,1],pi/4]); is_rhombus(S)

is_rhombus([2,2,0],[-2,2,0],[-2,-1,0],[2,-1,0])