code: def format_master_url(master, rpc_layer=None):
      if rpc_layer:
          return "%s://%s" % (rpc_layer, master)
      else:
          return master
  
imports: import abc
  import collections
  import six
  from tensorflow.python.client import session
  from tensorflow.python.eager import context
  from tensorflow.python.framework import config
  from tensorflow.python.framework import ops
  from tensorflow.python.training.server_lib import ClusterSpec
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 1 for calling a global function with example usage: format_master_url(master, rpc_layer) and returns: unknown, master