Find the bounding boxes for a given image file.

  Args:
    filenames: list of strings; each string is a path to an image file.
    image_to_bboxes: dictionary mapping image file names to a list of
      bounding boxes. This list contains 0+ bounding boxes.
  Returns:
    List of bounding boxes for each image. Note that each entry in this
    list might contain from 0+ entries corresponding to the number of bounding
    box annotations for the image.

def _find_image_bounding_boxes(filenames, image_to_bboxes):
  """Find the bounding boxes for a given image file.

  Args:
    filenames: list of strings; each string is a path to an image file.
    image_to_bboxes: dictionary mapping image file names to a list of
      bounding boxes. This list contains 0+ bounding boxes.
  Returns:
    List of bounding boxes for each image. Note that each entry in this
    list might contain from 0+ entries corresponding to the number of bounding
    box annotations for the image.
  """
  num_image_bbox = 0
  bboxes = []
  for f in filenames:
    basename = os.path.basename(f)
    if basename in image_to_bboxes:
      bboxes.append(image_to_bboxes[basename])
      num_image_bbox += 1
    else:
      bboxes.append([])
  print('Found %d images with bboxes out of %d images' % (
      num_image_bbox, len(filenames)))
  return bboxes