code: @Override
      public DescribeDBSubnetGroupsResult describeDBSubnetGroups(DescribeDBSubnetGroupsRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeDBSubnetGroups(request);
      }
docs: <p>
  Returns a list of DBSubnetGroup descriptions. If a DBSubnetGroupName is specified, the list will contain only the
  descriptions of the specified DBSubnetGroup.
  </p>
  <p>
  For an overview of CIDR ranges, go to the <a
  href="http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing">Wikipedia Tutorial</a>.
  </p>
  
  @param describeDBSubnetGroupsRequest
  @return Result of the DescribeDBSubnetGroups operation returned by the service.
  @throws DBSubnetGroupNotFoundException
  <i>DBSubnetGroupName</i> does not refer to an existing DB subnet group.
  @sample AmazonNeptune.DescribeDBSubnetGroups
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/neptune-2014-10-31/DescribeDBSubnetGroups" target="_top">AWS
  API Documentation</a>