code: def _checkCallSetIds(self, variantFile):
          
          if len(self._callSetIdMap) > 0:
              callSetIds = set([
                  self.getCallSetId(sample)
                  for sample in variantFile.header.samples])
              if callSetIds != set(self._callSetIdMap.keys()):
                  raise exceptions.InconsistentCallSetIdException(
                      variantFile.filename)
docs: Checks callSetIds for consistency