code: def l2(x, y):
      # technically squarred l2
      return tf.reduce_sum(
          tf.square(x - y), list(range(1, len(x.shape)))
      )
  
file_path: cleverhans/cleverhans/tf2/attacks/carlini_wagner_l2.py
imports: import numpy
  import tensorflow
  from cleverhans.tf2.utils import get_or_guess_labels, set_with_mask
label_desc: Use image node_id 2 for calling a global function with example usage: l2(x, y) and returns: tf