Coordinates of hand landmarks are not displayed in mediapipe hands

Question

I'm trying to create a dataset consisting of hand landmark coordinates obtained using mediapipe to train a neural network:

import cv2
import mediapipe
import sys
import os.path


signs = {'up': 0, 'down': 1, 'right': 2, 'left': 3}

drawingModule = mediapipe.solutions.drawing_utils
handsModule = mediapipe.solutions.hands

capture = cv2.VideoCapture(0)
frameWidth = capture.get(cv2.CAP_PROP_FRAME_WIDTH)
frameHeight = capture.get(cv2.CAP_PROP_FRAME_HEIGHT)

start = False
max_count = int(sys.argv[1])
counter = 0

with handsModule.Hands(static_image_mode=False, min_detection_confidence=0.7, min_tracking_confidence=0.7,
                       max_num_hands=1) as hands:
    while (True):
        # frame == 480 640
        ret, frame = capture.read()
        results = hands.process(cv2.cvtColor(frame, cv2.COLOR_BGR2RGB))
        cv2.rectangle(frame, (10, 30), (310, 330), (0, 255, 0), 2)
        k = cv2.waitKey(1)

        cv2.imshow('Test hand', frame)

        if counter == max_count:
            break

        if k == ord('u'):
            name = 'up'

        if k == ord('d'):
            name = 'down'

        if k == ord('r'):
            name = 'right'

        if k == ord('l'):
            name = 'left'

        if k == ord('a'):
            start = not start

        if start:
            data = []
            roi = frame[25:335, 8:315]
            hands_roi = hands.process(roi)
            counter += 1
            height, width, channels = roi.shape

            if hands_roi.multi_hand_landmarks != None:
                for handLandmarks in hands_roi.multi_hand_landmarks:
                    for point in handsModule.HandLandmark:
                        normalizedLandmark = handLandmarks.landmark[point]
                        pixelCoordinatesLandmark = drawingModule._normalized_to_pixel_coordinates(normalizedLandmark.x,
                                                                                              normalizedLandmark.y,
                                                                                              width, height)
                        print(pixelCoordinatesLandmark)

            if os.path.exists('dataset.csv'):
                columns = ['x11', 'x21', 'x12', 'x22', 'x13', 'x23', 'x14', 'x24', 'x15', 'x25',
                           'x16', 'x26', 'x17', 'x27', 'x18', 'x28', 'x19', 'x29', 'x110'
                           'x210', 'x111', 'x211', 'x112', 'x212', 'x113', 'x213', '114', '214', '115', 'x215',
                           'x116', 'x216', 'x117', 'x217', 'x118', 'x218', 'x119', 'x219', 'x120',
                           'x220', 'y']

        if k == ord('q'):
            break

cv2.destroyAllWindows()
capture.release()

But when I press 'a' and expect to get the coordinates of the hand landmarks I get nothing. How to fix it?⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀