'Returns bool that indicates if this variable is tainted.'

@property
def controlled_by_user(self):

    cbusr = self._controlled_by_user
    if (cbusr is None):
        if self.is_root:
            if (self._name in VariableDef.USER_VARS):
                cbusr = True
            else:
                cbusr = False
        else:
            cbusr = self.parent.controlled_by_user
        self._controlled_by_user = cbusr
    return cbusr
