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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _string_put_transform(cls, item, **kwargs):
        '''
        transfrom for a REG_SZ to properly handle "Not Defined"
        '''
        if isinstance(item, six.string_types):
            if item.lower() == 'not defined':
                return None
            else:
                return item