Where is CV_USRTYPE1 depth param on Python dir(cv2)?

I can't find CV_USRTYPE1 on Python, however, It is possible to enum all other depths with dir(cv2).

The following code:

import cv2
import re


depths = [i for i in dir(cv2) if re.search('^CV_(?:\d+[A-Z]{1}|USRTYPE1)$', i, re.IGNORECASE)]
print(depths)

Returns:

['CV_16S', 'CV_16U', 'CV_32F', 'CV_32S', 'CV_64F', 'CV_8S', 'CV_8U']

Where is CV_USRTYPE1? Or is there another way to get the depths?

Is it something related to this? That CV_16F was added and CV_USRTYPE1 is legacy?