code: def get_layout_prefix_len(layout, prefix):
      for i, c in enumerate(layout):
          if c not in prefix:
              return i
      return len(layout)
  
imports: import os
  import random
  import numpy
  from typing import List, Union, Callable, Optional
  from dataclasses import dataclass, field
  from nvidia.dali import pipeline_def
  import nvidia.dali.fn
  from nvidia.dali import types
  import nvidia.dali.tensors
  from test_utils import get_dali_extra_path, check_batch
label_desc: Use image node_id 6 for calling a global function with example usage: get_layout_prefix_len(layout, prefix) and returns: len, i