code: @Override
      public DescribeExpressionsResult describeExpressions(DescribeExpressionsRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeExpressions(request);
      }
docs: <p>
  Gets the expressions configured for the search domain. Can be limited to specific expressions by name. By
  default, shows all expressions and includes any pending changes to the configuration. Set the
  <code>Deployed</code> option to <code>true</code> to show the active configuration and exclude pending changes.
  For more information, see <a
  href="http://docs.aws.amazon.com/cloudsearch/latest/developerguide/configuring-expressions.html"
  target="_blank">Configuring Expressions</a> in the <i>Amazon CloudSearch Developer Guide</i>.
  </p>
  
  @param describeExpressionsRequest
  Container for the parameters to the <code><a>DescribeDomains</a></code> operation. Specifies the name of
  the domain you want to describe. To restrict the response to particular expressions, specify the names of
  the expressions you want to describe. To show the active configuration and exclude any pending changes,
  set the <code>Deployed</code> option to <code>true</code>.
  @return Result of the DescribeExpressions operation returned by the service.
  @throws BaseException
  An error occurred while processing the request.
  @throws InternalException
  An internal error occurred while processing the request. If this problem persists, report an issue from
  the <a href="http://status.aws.amazon.com/" target="_blank">Service Health Dashboard</a>.
  @throws ResourceNotFoundException
  The request was rejected because it attempted to reference a resource that does not exist.
  @sample AmazonCloudSearch.DescribeExpressions