class AliTPCQAChecker: public AliQACheckerBase

 It is important to understand the destinction between indexed tasks (AliQAv1::TASKINDEX_t) which are used in the DataMaker classes and indexed tasks (AliQAv1::ALITASK_t) whihc are used in the checker class.

     From the AliQAChecker::Run() methods we have:
     AliQAv1::kRAW
     - AliQAv1::kRAWS

     AliQAv1::kSIM
     - AliQAv1::kHITS
     - AliQAv1::kSDIGITS
     - AliQAv1::kDIGITS

     AliQAv1::kREC
     - AliQAv1::kDIGITSR
     - AliQAv1::kRECPOINTS
     - AliQAv1::kTRACKSEGMENTS
     - AliQAv1::kRECPARTICLES

     AliQAv1::kESD ;
     -AliQAv1::kESDS

     This means that for each group of tasks the Check will be called
     one or more times.  This also mean that we cannot know what
     histograms will be or not be there in a single call... And we
     also do not know the position in the list of the histogram.

 Check ESD

 This method checks the QA histograms associated with simulation

 For TPC this is:
 Digits :
 The digit histogram gives the ADC distribution for all sigbnals
 above threshold. The check is just that there are digits.
 Hits : The hit histograms are checked to see that they are not
 empty. They contain a lot of detailed information on the
 energyloss model (they were used to debug the AliRoot TPC use of
 FLUKA).

 The check methods are simple:
 We do not know if it is bad that histograms are missing because
 this will always be the case for summable digits. So this check
 is not possible here.
 If digit histogram is empty (set error)
 If one of the hit histograms are empty (set error)

 This method checks the QA histograms associated with reconstruction

 For TPC this is:
 DigitsR :
 The digit histogram gives the ADC distribution for all sigbnals
 above threshold. The check is just that there are digits.
 RecPoints :
 The cluster histograms are meant to give an idea about the gain
 from the cluster charge and to indicate iof there are rows with
 noise clusters, i.e., they are very visual.

 The check methods are simple:
 If there are no histogram at all (set fatal)
 If digit histogram is there, but there are no digits (set error)
 If cluster histogram is there but there are less than 1000
    clusters (set warning)
 If there are more than 1000 clusters but no clusters for either short,
 medium, or long pads (set error)

 This method checks the QA histograms associated with ESDs
 (Note that there is aslo a globalQA which is running on all
  the ESD information so for now this is just a few basic
  histograms)

 The check methods are simple:
 If there are no histogram at all (set fatal)

 intialises QA and QA checker settings

 sets the QA according the return value of the Check