code: def channel(layer, n_channel, batch=None):
      """Visualize a single channel"""
  
      @handle_batch(batch)
      def inner(T):
          return tf.reduce_mean(T(layer)[..., n_channel])
  
      return inner
  
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 4 for calling a global function with example usage: channel(layer, n_channel, batch) and returns: inner, tf