code: def verify(self, windowSize=None):
          
          if self.rowCount() == 0:
              return "Protocol must have at least one test"
          if self.caldb is None or self.calv is None:
              return "Protocol reference voltage not set"
          for test in self._tests:
              msg = test.verify(windowSize)
              if msg:
                  return msg
          return 0
docs: Verify that this protocol model is valid. Return 0 if sucessful,
          a failure message otherwise
  
          :param windowSize: acquistion window size (seconds), to check against duration, check is not performed is None provided
          :type windowSize: float
          :returns: 0 (int) for success, fail message (str) otherwise