plot3d(
    cos((x**2 + y**2)), (x, -pi, pi), (y, -pi, pi),
    x_ticks_formatter=multiples_of_pi_over_2(),
    y_ticks_formatter=multiples_of_pi_over_2(),
)
# Expected:
## Plot object containing:
## [0]: cartesian surface: cos(x**2 + y**2) for x over (-pi, pi) and y over (-pi, pi)