code: def ensure_concrete_host(host, default_host=None):
      """
      Ensure the given host string (or IP) denotes a concrete host, not a
      wildcard listening address.
      """
      if host in ("0.0.0.0", ""):
          return default_host or get_ip()
      elif host == "::":
          return default_host or get_ipv6()
      else:
          return host
  
file_path: distributed/distributed/comm/utils.py
imports: from __future__ import annotations
  import logging
  import socket
  import dask
  from dask.utils import parse_bytes
  from distributed import protocol
  from distributed.sizeof import safe_sizeof
  from distributed.utils import get_ip, get_ipv6, nbytes, offload
label_desc: Use image node_id 3 for calling a global function with example usage: ensure_concrete_host(host, default_host) and returns: unknown, unknown, host