code: public InfraAlertConditionCache infraAlertConditions(long policyId)
      {
          InfraAlertConditionCache cache = infraConditions.get(policyId);
          if(cache == null)
              infraConditions.put(policyId, cache = new InfraAlertConditionCache(policyId));
          return cache;
      }
docs: Returns the cache of Infrastructure alert conditions for the given policy, creating one if it doesn't exist .
  @param policyId The id of the policy for the cache of Infrastructure alert conditions
  @return The cache of Infrastructure alert conditions for the given policy