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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_changeset(self, changeset_id: uuid.UUID) -> None: """ Checks to be sure the changeset is known by the journal """

        if not self.journal.has_changeset(changeset_id):
            raise ValidationError("Changeset not found in journal: {0}".format(
                str(changeset_id)
            ))