Assignment Collection for y[0,0,0] is usually not very helpful.
New representation:
In [6]: forward_assignments = pystencils.AssignmentCollection({
...: z[0, 0]: x[0, 0] * sympy.log(x[0, 0] * y[0, 0]),
...: y[0,0] : x[1,1] +1
...: })
In [7]: forward_assignments
Out[7]: AssignmentCollection: z_C, y_C <- f(x_C, x_NE)