[Zope] class Missing.Missing help

Hello All, I have a ZSQL method executing a simple 'select' statement against a MS SQL Server. Some of the rows/columns have missing values. On looking at the variable 'type', I get - <extension class Missing.Missing at 013130E0> How do I test if the return value is a NULL value? e.g., as in if variable is None: do something... If I assign this value to a variable in a dictionary, I get - {'variable':Missing.Value} Help much appreciated. Thx. Regards, Samir