import numpy as np
f = lambda x, y: np.sin(2 * x + 2 * y)
fx = lambda x, y: np.cos(f(x, y))
fy = lambda x, y: np.sin(f(x, y))
graphics(
    vector_field_2d(fx, fy, ("x", -1, 1), ("y", -1, 1),
        streamlines=True, scalar=False, use_cm=False),
    aspect="equal", xlabel="x", ylabel="y", grid=False
)  # doctest: +SKIP