code: def getWorksheet(self):
          
          worksheet = self.getBackReferences('WorksheetAnalysis')
          if not worksheet:
              return None
          if len(worksheet) > 1:
              logger.error(
                  "Analysis %s is assigned to more than one worksheet."
                  % self.getId())
          return worksheet[0]
docs: Returns the Worksheet to which this analysis belongs to, or None