code: def get_channel_index(data_format=INVALID):
      assert data_format != INVALID
      axis = 3 if data_format == "NHWC" else 1
      return axis
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import tensorflow
label_desc: Use image node_id 2 for calling a global function with example usage: get_channel_index(data_format) and returns: axis