in here I get error for roi it is 'inconsistent use of tabs and spaces in indentation '

edit

Code:

import numpy as np
import cv2

face_cascade = cv2.CascadeClassifier('cascades/data/haarcascade_frontalface_alt2.xml')


cap = cv2.VideoCapture(0)

while(True):

    ret,frame = cap.read()
    gray  = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, scaleFactor=1.5, minNeighbors=5)
    for (x, y, w, h) in faces:
        print(x,y,w,h)
        roi

    cv2.imshow('frame',frame)
    if cv2.waitKey(20) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()