def _is_valid(self):
    if self.sas.exist(self.table, self.libref):
        return None
    else:
        msg = (((('The SAS Data Set that this SASdata object refers to, ' + self.libref) + '.') + self.table) + ', does not exist in this SAS session at this time.')
        ll = {'LOG': msg, 'LST': msg}
        return ll
def _is_valid(self):
    if self.sas.exist(self.table, self.libref):
        return None
    else:
        msg = (((('The SAS Data Set that this SASdata object refers to, ' + self.libref) + '.') + self.table) + ', does not exist in this SAS session at this time.')
        ll = {'LOG': msg, 'LST': msg}
        return ll