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