新入门找的一段代码求讲解

[四季酒店]

# This import registers the 3D projection, but is otherwise unused.
from mpl_toolkits.mplot3d import Axes3D # noqa: F401 unused import

from matplotlib import cbook
from matplotlib import cm
from matplotlib.colors import LightSource
import matplotlib.pyplot as plt
import numpy as np

# Load and format data
filename = cbook.get_sample_data('jacksboro_fault_dem.npz', asfileobj=False)
with np.load(filename) as dem:
z = dem['elevation']
nrows, ncols = z.shape
x = np.linspace(dem['xmin'], dem['xmax'], ncols)
y = np.linspace(dem['ymin'], dem['ymax'], nrows)
x, y = np.meshgrid(x, y)

region = np.s_[5:50, 5:50]
x, y, z = x[region], y[region], z[region]



plt.show()


主要是loda data这段， dem['elevation'] ，dem['xmin'], dem['xmax']，对应的txt应该是什么样的？想看一下效果。
还有region = np.s_[5:50, 5:50]和cbook.get_sample_data('jacksboro_fault_dem.npz', asfileobj=False)是什么意思，求大神讲解一下，谢谢

[四季酒店]

这个读取的大概是一个 包含xyz数据的txt，具体格式是什么样子的