$ x=2-\frac{z}{2} $

$ x=\frac{z}{2} $

$ y=2-z $

$ y=z-2 $

A = (1.5, 1)
B = (0.5, 1)
C = (0.5, -1)
D = (1.5, -1)
poly1, a, b, c, d = Polygon(A, B, C, D)