code: @Override
      public DescribeCacheSubnetGroupsResult describeCacheSubnetGroups(DescribeCacheSubnetGroupsRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeCacheSubnetGroups(request);
      }
docs: <p>
  Returns a list of cache subnet group descriptions. If a subnet group name is specified, the list contains only
  the description of that group.
  </p>
  
  @param describeCacheSubnetGroupsRequest
  Represents the input of a <code>DescribeCacheSubnetGroups</code> operation.
  @return Result of the DescribeCacheSubnetGroups operation returned by the service.
  @throws CacheSubnetGroupNotFoundException
  The requested cache subnet group name does not refer to an existing cache subnet group.
  @sample AmazonElastiCache.DescribeCacheSubnetGroups
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/elasticache-2015-02-02/DescribeCacheSubnetGroups"
  target="_top">AWS API Documentation</a>