code: def mock_bitmap(mock_image):
      bitmap = np.squeeze(
          cv2.cvtColor(mock_image, cv2.COLOR_BGR2GRAY) / 255.0
      )
      bitmap = np.expand_dims(bitmap, axis=-1)
      return bitmap
  
file_path: doctr/tests/common/test_models.py
imports: from io import BytesIO
  import cv2
  import numpy
  import pytest
  import requests
  from doctr.io import reader
  from doctr.models._utils import estimate_orientation, get_language, invert_data_structure
  from doctr.utils import geometry
label_desc: Use image node_id 2 for calling a global function with example usage: mock_bitmap(mock_image) and returns: bitmap