def __init__ ( self, allow_none = False ):
        if allow_none:
            self.validate      = self.validate_none
            self.info          = self.info_none
            self.fast_validate = ( 2, None )
        else:
            self.fast_validate = ( 2, )
Creates a ThisClass handler.
dataset/ETHPy150Open enthought/traits/traits/trait_handlers.py/ThisClass.__init__