当我使用渐近plot_implicit时，我如何显示一个窗口？

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
from sympy import symbols, plot_implicit

x, y, z = symbols('x y z')
expr = x**2 + y**2 + z**2 - 1

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

plot = plot_implicit(expr, (x, -1, 1), (y, -1, 1), (z, -1, 1), ax=ax)

plt.show()

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
from sympy import symbols, plot_implicit

x, y, z = symbols('x y z')
expr = x**2 + y**2 + z**2 - 1

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

plot = plot_implicit(expr, (x, -1, 1), (y, -1, 1), (z, -1, 1), ax=ax)

plt.show()