@Override
    public DescribeDBInstancesResult apply(DescribeDBInstancesRequest describeDBInstancesRequest) {
        return client.describeDBInstances(describeDBInstancesRequest);
    }
Makes a call to the operation specified by the waiter by taking the corresponding request and returns the
corresponding result

@param describeDBInstancesRequest
       Corresponding request for the operation
@return Corresponding result of the operation
aws-java-sdk-neptune/src/main/java/com/amazonaws/services/neptune/waiters/DescribeDBInstancesFunction.java