code: def open(f, mode=None):
      if mode is None:
          if hasattr(f, "mode"):
              mode = f.mode
          else:
              mode = "rb"
      if mode in ("r", "rb"):
          return Au_read(f)
      elif mode in ("w", "wb"):
          return Au_write(f)
      else:
          raise Error("mode must be 'r', 'rb', 'w', or 'wb'")
  
imports: from collections import namedtuple
  import warnings
label_desc: Use image node_id 3 for calling a global function with example usage: open(f, mode) and returns: Au_read, Au_write