code: def L2(layer="input", constant=0, epsilon=1e-6):
      """L2 norm of layer. Generally used as penalty."""
      return lambda T: tf.sqrt(
          epsilon + tf.reduce_sum((T(layer) - constant) ** 2)
      )
  
imports: from __future__ import absolute_import, division, print_function
  from decorator import decorator
  import numpy
  import tensorflow
  from lucid.optvis.objectives_util import _dot, _dot_cossim, _extract_act_pos, _make_arg_str, _T_force_NHWC, _T_handle_batch
label_desc: Use image node_id 11 for calling a global function with example usage: L2(layer, constant, epsilon) and returns: function