docstr: MTCNN detects invalid images
  :return:
code: def test_detect_faces_invalid_content(self):
      """
      MTCNN detects invalid images
      :return:
      """
      ivan = cv2.imread("example.py")
  
      with self.assertRaises(InvalidImage):
          result = mtcnn.detect_faces(ivan)
  
file_path: mtcnn/tests/test_mtcnn.py
imports: import unittest
  import cv2
  from mtcnn.exceptions import InvalidImage
  from mtcnn import MTCNN
label_desc: Use image node_id 3 for calling the TestMTCNN obj's underlying member method code with example usage: obj.test_detect_faces_invalid_content() without return types