plot_real_imag(sqrt(x), (x, -3-3j, 3+3j),
    n=100, real=False, imag=False, abs=True, threed=True)
# Expected:
## Plot object containing:
## [0]: complex cartesian surface: abs(sqrt(x)) for re(x) over (-3.0, 3.0) and im(x) over (-3.0, 3.0)