code: def GetHostname(self, session_identifier=CURRENT_SESSION):
      
      hostname_artifact = self._hostnames.get(session_identifier, None)
      if not hostname_artifact:
        return ''
  
      return hostname_artifact.name or ''
docs: Retrieves the hostname related to the event.
  
      If the hostname is not stored in the event it is determined based
      on the preprocessing information that is stored inside the storage file.
  
      Args:
        session_identifier (Optional[str])): session identifier, where
            CURRENT_SESSION represents the active session.
  
      Returns:
        str: hostname.