code: def bbox_area(bbox, is_bbox_normalized):
      """
      Calculate area of a bounding box
      """
      norm = 1.0 - float(is_bbox_normalized)
      width = bbox[2] - bbox[0] + norm
      height = bbox[3] - bbox[1] + norm
      return width * height
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import os
  import sys
  import numpy
  import itertools
  import paddle
  from ppdet.modeling.rbox_utils import poly2rbox_np
  from ppdet.utils.logger import setup_logger
label_desc: Use image node_id 2 for calling a global function with example usage: bbox_area(bbox, is_bbox_normalized) and returns: unknown