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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 validate(self, val):
 """ For a val to pass validation, it must have a _tag set. This assumes that the object validated that _tag is a valid tag, and that any associated value has also been validated. """

        self.validate_type_only(val)
        if not hasattr(val, '_tag') or val._tag is None:
            raise ValidationError('no tag set')
        return val