code: @Override
      public DescribeThingGroupResult describeThingGroup(DescribeThingGroupRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeThingGroup(request);
      }
docs: <p>
  Describe a thing group.
  </p>
  
  @param describeThingGroupRequest
  @return Result of the DescribeThingGroup operation returned by the service.
  @throws InvalidRequestException
  The request is not valid.
  @throws ThrottlingException
  The rate exceeds the limit.
  @throws InternalFailureException
  An unexpected error has occurred.
  @throws ResourceNotFoundException
  The specified resource does not exist.
  @sample AWSIot.DescribeThingGroup