code: @Override
      public EventSubscription modifyEventSubscription(ModifyEventSubscriptionRequest request) {
          request = beforeClientExecution(request);
          return executeModifyEventSubscription(request);
      }
docs: <p>
  Modifies an existing event notification subscription. Note that you can't modify the source identifiers using
  this call; to change source identifiers for a subscription, use the <a>AddSourceIdentifierToSubscription</a> and
  <a>RemoveSourceIdentifierFromSubscription</a> calls.
  </p>
  <p>
  You can see a list of the event categories for a given SourceType by using the <b>DescribeEventCategories</b>
  action.
  </p>
  
  @param modifyEventSubscriptionRequest
  @return Result of the ModifyEventSubscription operation returned by the service.
  @throws EventSubscriptionQuotaExceededException
  @throws SubscriptionNotFoundException
  @throws SNSInvalidTopicException
  @throws SNSNoAuthorizationException
  @throws SNSTopicArnNotFoundException
  @throws SubscriptionCategoryNotFoundException
  @sample AmazonNeptune.ModifyEventSubscription
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/neptune-2014-10-31/ModifyEventSubscription"
  target="_top">AWS API Documentation</a>