code: def addExpression(self, datafields):
          
          self._expressionValueList.append(datafields)
          if len(self._expressionValueList) >= self._batchSize:
              self.batchAddExpression()
docs: Adds an Expression to the db.  Datafields is a tuple in the order:
          id, rna_quantification_id, name, expression,
          is_normalized, raw_read_count, score, units, conf_low, conf_hi