code: def merge_roidb(roidbs):
      """roidb are list, concat them together"""
      roidb = roidbs[0]
      for r in roidbs[1:]:
          roidb.extend(r)
      return roidb
  
file_path: insightface/detection/retinaface/rcnn/utils/load_data.py
imports: import numpy
  from ..logger import logger
  from ..config import config
  from ..dataset import *
label_desc: Use image node_id 3 for calling a global function with example usage: merge_roidb(roidbs) and returns: roidb