code: def normalize_data_format(value):
      data_format = value.lower()
      if data_format not in {"channels_first", "channels_last"}:
          raise ValueError(
              "The `data_format` argument must be one of "
              '"channels_first", "channels_last". Received: '
              f"{str(value)}."
          )
      return data_format
  
file_path: tensorflow/tensorflow/python/layers/utils.py
imports: from tensorflow.python.framework import smart_cond
  from tensorflow.python.ops import cond
  from tensorflow.python.ops import variables
label_desc: Use image node_id 3 for calling a global function with example usage: normalize_data_format(value) and returns: data_format