class_docstr: Store information on generated alerts.
code: def __init__(self, staged_at, staged_until, current_time, rule):
      self._rule_name = rule
      self._current_time = current_time
      self._staged_at = staged_at
      self.staged_until = staged_until
      self.alert_count = self._ALERT_COUNT_UNKOWN
      self.execution_id = None
  
file_path: streamalert/streamalert/rule_promotion/statistic.py
label_desc: Use image node_id 1 to create a new StagingStatistic object  with example: obj = StagingStatistic(staged_at, staged_until, current_time, rule)