1 | initial version |

This is because all these posets are "facade". Try something like that :

```
sage: P=Posets(4)
sage: Q=next(iter(P))
sage: Q._is_facade
True
sage: Permutation(x+1 for x in Q.linear_extension())
[4, 3, 2, 1]
```

2 | No.2 Revision |

This is because all these posets are "facade". Try something like that :

`sage: `~~P=Posets(4)
~~P = Posets(4)
sage: ~~Q=next(iter(P))
~~Q = next(iter(P))
sage: Q._is_facade
True
sage: Permutation(x+1 for x in Q.linear_extension())
[4, 3, 2, 1]

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