code: def _has_ipv6(host):
      
      sock = None
      has_ipv6 = False
  
      # App Engine doesn't support IPV6 sockets and actually has a quota on the
      # number of sockets that can be used, so just early out here instead of
      # creating a socket needlessly.
      # See https://github.com/urllib3/urllib3/issues/1446
      if _appengine_environ.is_appengine_sandbox():
          return False
  
      if socket.has_ipv6:
          # has_ipv6 returns true if cPython was compiled with IPv6 support.
          # It does not tell us if the system has IPv6 support enabled. To
          # determine that we must bind to an IPv6 address.
          # https://github.com/shazow/urllib3/pull/611
          # https://bugs.python.org/issue658327
          try:
              sock = socket.socket(socket.AF_INET6)
              sock.bind((host, 0))
              has_ipv6 = True
          except Exception:
              pass
  
      if sock:
          sock.close()
      return has_ipv6
docs: Returns True if the system can bind an IPv6 address.