Python OpenCV fails using haarscascade

Question

Any suggestions how to fix this - its my first attempt as OpenCV.

[ERROR:[email protected]] global persistence.cpp:505 open Can't open file: 'haarcascade_upperbody.xml' in read mode
Traceback (most recent call last):
  File "/home/peter/src/personid/./2.py", line 13, in <module>
    body = cascade.detectMultiScale(
cv2.error: OpenCV(4.7.0) /io/opencv/modules/objdetect/src/cascadedetect.cpp:1689: error: (-215:Assertion failed) !empty() in function 'detectMultiScale'

Check file exists****************************************************************** .local/lib/python3.10/site-packages/cv2/data:- -rw-rw-r-- 1 peter peter 785819 May 4 16:23 haarcascade_upperbody.xml VERSIONS********************************************************************* python -V:- Python 3.10.6 Linux 5.15.0-71-generic #78-Ubuntu SMP CODE***********************************************************************

import cv2
import numpy as np
cascade = cv2.CascadeClassifier('haarcascade_upperbody.xml');
image = cv2.imread('/home/peter/Pictures/2018/08/03/PC030071.JPG')
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY);
body = cascade.detectMultiScale(
    gray,
    scaleFactor = 1.1,
    minNeighbors = 5,
    minSize = (30,30),
    flags = cv2.CASCADE_SCALE_IMAGE
)

Run code, expected count of matching "upperbodies" and images - code for this output not included for brevity Error occurred as shown. Traceback refers to last statement, but fails on opening a standard file - which exists as expected.