code: def flatten_list(l):
      """Flatten a 2D list"""
      return sum(l, [])
  
imports: import xml.etree.ElementTree
  from collections import OrderedDict
  import json
  import struct
  import imghdr
  import numpy
  from .geom import pt, rect
label_desc: Use image node_id 17 for calling a global function with example usage: flatten_list(l) and returns: sum