when loading custom ply using the steps from tanks it doesn't get color

[AndreV84]

`python3
Python 3.6.9 (default, Oct 8 2020, 12:12:24)
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

import numpy as np
import pptk
import plyfile
data = plyfile.PlyData.read('cloud.ply')['vertex']
xyz = np.c_[data['x'], data['y'], data['z']]
rgb = np.c_[data['red'], data['green'], data['blue']]
n = np.c_[data['nx'], data['ny'], data['nz']]
Traceback (most recent call last):
File "", line 1, in
File "/home/nvidia/.local/lib/python3.6/site-packages/plyfile.py", line 770, in getitem
return self.data[key]
File "/home/nvidia/.local/lib/python3.6/site-packages/numpy/core/memmap.py", line 331, in getitem
res = super(memmap, self).getitem(index)
ValueError: no field of name nx`

[AndreV84]

could you also extend on the installation issuees, please?
https://forums.developer.nvidia.com/t/building-pptk-on-xavier-how-to-get-through/160079