code: def flatten(self):
      i = 0
      L = copy.deepcopy(self._items)
      while i < len(L):
          while isinstance(L[i], Group) and len(L[i]._items):
              L[i : i + 1] = L[i]._items
          i += 1
      return L
  
file_path: vispy/vispy/util/svg/group.py
imports: import copy
  from ...util import logger
  from .path import Path
  from .base import namespace
  from .transformable import Transformable
label_desc: Use image node_id 2 for calling the Group obj's underlying member method code with example usage: obj.flatten() and returns: L