(generate_type_2_vertices_general) Rework,
the meaning of (x,y,z,xeps,yeps,zeps) is consistent even if reduced=True
(finite_dimensional_extremality_test_general): returns True/False.
For discontinuous functions:
1) need to provide covered_intervals;
2) Perturbation plotting is not ready yet.
(random_piecewise_function): can generate discontinuous function