code: def get_opencv_requirement():
      """
      Return the OpenCV requirement string.
      Since opencv library is distributed in several independent packages,
      we first check whether any form of opencv is already installed. If not,
      we choose between opencv-python vs opencv-python-headless version based
      on the environment.
      For headless environment (Docker, Colab & Kaggle notebooks), we install
      opencv-python-headless; otherwise - default to opencv-python.
      """
      try:
          import cv2
  
          return []
      except ImportError:
          default_requirement = "opencv-python>=4.1"
          headless_requirement = "opencv-python-headless>=4.1"
  
          if is_docker() or is_kaggle() or is_colab():
              return [headless_requirement]
          else:
              return [default_requirement]
  
file_path: pytorch-toolbelt/setup.py
imports: import ast
  import io
  import re
  import os
  import sys
  from setuptools import find_packages, setup
  from distutils.version import LooseVersion
label_desc: Use image node_id 4 for calling a global function with example usage: get_opencv_requirement() and returns: list, list, list