code: def _get_candidates(self, all_rules):
          
          candidates = []
          for rule in all_rules:
              if rule.ever_matched() and rule.time_to_report():
                  candidates.append(rule)
          return candidates
docs: Don't report a rule statistics if any of the conditions is met:
          1. The report time hasn't come(some rules might have larger report intervals).
          2. The rule is never matched.