code: @Override
      public ReplicationGroup decreaseReplicaCount(DecreaseReplicaCountRequest request) {
          request = beforeClientExecution(request);
          return executeDecreaseReplicaCount(request);
      }
docs: <p>
  Dynamically decreases the number of replics in a Redis (cluster mode disabled) replication group or the number of
  replica nodes in one or more node groups (shards) of a Redis (cluster mode enabled) replication group. This
  operation is performed with no cluster down time.
  </p>
  
  @param decreaseReplicaCountRequest
  @return Result of the DecreaseReplicaCount operation returned by the service.
  @throws ReplicationGroupNotFoundException
  The specified replication group does not exist.
  @throws InvalidReplicationGroupStateException
  The requested replication group is not in the <code>available</code> state.
  @throws InvalidCacheClusterStateException
  The requested cluster is not in the <code>available</code> state.
  @throws InvalidVPCNetworkStateException
  The VPC network is in an invalid state.
  @throws InsufficientCacheClusterCapacityException
  The requested cache node type is not available in the specified Availability Zone.
  @throws ClusterQuotaForCustomerExceededException
  The request cannot be processed because it would exceed the allowed number of clusters per customer.
  @throws NodeGroupsPerReplicationGroupQuotaExceededException
  The request cannot be processed because it would exceed the maximum allowed number of node groups
  (shards) in a single replication group. The default maximum is 15
  @throws NodeQuotaForCustomerExceededException
  The request cannot be processed because it would exceed the allowed number of cache nodes per customer.
  @throws ServiceLinkedRoleNotFoundException
  The specified service linked role (SLR) was not found.
  @throws NoOperationException
  The operation was not performed because no changes were required.
  @throws InvalidParameterValueException
  The value for a parameter is invalid.
  @throws InvalidParameterCombinationException
  Two or more incompatible parameters were specified.
  @sample AmazonElastiCache.DecreaseReplicaCount
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/elasticache-2015-02-02/DecreaseReplicaCount"
  target="_top">AWS API Documentation</a>