python 中如何取出colomap部分的颜色范围

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
import numpy as np
from matplotlib.colors import ListedColormap, LinearSegmentedColormap
ax = plt.subplot()
cmap=plt.get_cmap('jet')
newcolors=cmap(np.linspace(0, 1, 256))
newcmap = ListedColormap(newcolors[57:245])
im = ax.imshow(np.arange(100).reshape((10, 10)),cmap=newcmap)
# create an axes on the right side of ax. The width of cax will be 5%
# of ax and the padding between cax and ax will be fixed at 0.05 inch.
divider = make_axes_locatable(ax)
cax = divider.append_axes("right", size="5%", pad=0.05)
plt.colorbar(im, cax=cax)
plt.show()