code: def getNumberOfQCSamples(self):
          
          qc_analyses = self.getQCAnalyses()
          qc_samples = [a.getSample().UID() for a in qc_analyses]
          # discarding any duplicate values
          return len(set(qc_samples))
docs: Returns the number of Quality Control samples.
          :returns: number of QC samples
          :rtype: integer