def METHOD_NAME(self) -> None:
    """Tests implementation of flatten(), which should do find on all keys"""
    self.union_find.add(1)
    self.union_find.union(3, 2)
    self.union_find.union(7, 5)
    self.union_find.union(2, 1)
    self.union_find.union(4, 2)
    self.union_find.union(5, 2)
    self.union_find.union(6, 5)
    self.union_find.add(14)
    self.union_find.union(14, 12)
    self.union_find.union(15, 13)
    self.union_find.union(16, 11)
    self.union_find.union(15, 14)
    self.union_find.union(16, 17)
    self.union_find.union(13, 11)
    self.assertEqual(self.union_find._representative_dict[1], 1)
    self.assertEqual(self.union_find._representative_dict[2], 1)
    self.assertEqual(self.union_find._representative_dict[3], 2)
    self.assertEqual(self.union_find._representative_dict[4], 1)
    self.assertEqual(self.union_find._representative_dict[5], 1)
    self.assertEqual(self.union_find._representative_dict[6], 1)
    self.assertEqual(self.union_find._representative_dict[7], 5)
    self.assertEqual(self.union_find._representative_dict[11], 17)
    self.assertEqual(self.union_find._representative_dict[12], 17)
    self.assertEqual(self.union_find._representative_dict[13], 12)
    self.assertEqual(self.union_find._representative_dict[14], 12)
    self.assertEqual(self.union_find._representative_dict[15], 13)
    self.assertEqual(self.union_find._representative_dict[16], 11)
    self.assertEqual(self.union_find._representative_dict[17], 17)
    self.union_find.flatten()
    self.assertEqual(self.union_find._representative_dict[1], 1)
    self.assertEqual(self.union_find._representative_dict[2], 1)
    self.assertEqual(self.union_find._representative_dict[3], 1)
    self.assertEqual(self.union_find._representative_dict[4], 1)
    self.assertEqual(self.union_find._representative_dict[5], 1)
    self.assertEqual(self.union_find._representative_dict[6], 1)
    self.assertEqual(self.union_find._representative_dict[7], 1)
    self.assertEqual(self.union_find._representative_dict[11], 17)
    self.assertEqual(self.union_find._representative_dict[12], 17)
    self.assertEqual(self.union_find._representative_dict[13], 17)
    self.assertEqual(self.union_find._representative_dict[14], 17)
    self.assertEqual(self.union_find._representative_dict[15], 17)
    self.assertEqual(self.union_find._representative_dict[16], 17)
    self.assertEqual(self.union_find._representative_dict[17], 17)