code: def flatten_tree(tree):
      """Flattens a nested structure to a list."""
      return tf.nest.flatten(tree)
  
imports: import functools
  import numpy
  import six
  import tensorflow.compat.v2
  from tensorflow.python.util import nest
label_desc: Use image node_id 2 for calling a global function with example usage: flatten_tree(tree) and returns: tf