我可以将黑网线添加到热卡部分 python Altair?

stroke

rect

import altair as alt

import numpy as np

import pandas as pd



# Compute x^2 + y^2 across a 2D grid

x, y = np.meshgrid/range/-5, 5/, range/-5, 5//

z = x ** 2 + y ** 2



# Convert this grid to columnar data expected by Altair

source = pd.DataFrame/{'x': x.ravel//,

 'y': y.ravel//,

 'z': z.ravel//}/



alt.Chart/source/.mark_rect/stroke='black', strokeWidth=2/.encode/

 x='x:O',

 y='y:O',

 color='z:Q'

/