docstr: Ends the cooldown period and moves this host out of blacklist.
docstr_tok: ["Ends","the","cooldown","period","and","moves","this","host","out","of","blacklist","."]
code: def whitelist(self):
      """Ends the cooldown period and moves this host out of blacklist."""
      self._cooldown_period_end_ts = 0
      self._blacklisted = False
  
imports: import io
  import logging
  import random
  import threading
  import time
  from collections import defaultdict
  from horovod.runner.common.util import safe_shell_exec
  from horovod.runner.elastic.worker import HostUpdateResult
label_desc: Use image node_id 8 for calling the HostState obj's underlying member method code with example usage: obj.whitelist() without return types