docs: def last_cache(self,result='COMPLETE'):
          """
          The date and time of the previous cache.
  
          Parameters
          ----------
          result : string, default 'COMPLETE'
              A string to choose which point in the log,
              should be returned.
              - COMPLETE - the last time a cache was completed
              - STARTED - the last time a cache was started
          Returns
          -------
          datetime.datetime
  
          """
          crit = and_(SymbolLogEvent.event == 'CACHE',
                      SymbolLogEvent.evresult == result)
          qry = self.log.filter(crit)
          qry = qry.order_by(SymbolLogEvent.evtime.desc())
          
          t = qry.first()
          
          if t:
              return t.evtime
          else:
              return None