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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 clean(self):
 """ Validates the forum instance. """

        super().clean()

        if self.parent and self.parent.is_link:
            raise ValidationError(_('A forum can not have a link forum as parent'))

        if self.is_category and self.parent and self.parent.is_category:
            raise ValidationError(_('A category can not have another category as parent'))

        if self.is_link and not self.link:
            raise ValidationError(_('A link forum must have a link associated with it'))