15 | | - no vertices and rays (the cone can only be initialized from Hrep), |

16 | | - multiple lines (they are being recomputed and there is no guarantee that they appear in the same order). |

| 15 | - the empty polyhedron (cone is `None` in this case). |

| 16 | |

| 17 | As the lines are recomputed, there is no guarantee that they appear in the same order in the normaliz cone. However, normaliz sorts the given lines anyway: |

| 18 | {{{ |

| 19 | sage: P = Polyhedron(lines=[[1,0], [0,1]], backend='normaliz').lines() |

| 20 | (A line in the direction (1, 0), A line in the direction (0, 1)) |

| 21 | sage: P = Polyhedron(lines=[[0,1], [1,0]], backend='normaliz').lines() |

| 22 | (A line in the direction (1, 0), A line in the direction (0, 1)) |

| 23 | sage: P = Polyhedron(lines=[[1,1], [1,0]], backend='normaliz').lines() |

| 24 | (A line in the direction (1, 0), A line in the direction (0, 1)) |

| 25 | }}} |

| 26 | |

| 27 | Also, even if `_normaliz_cone` has the lines somewhat shuffled, this shouldn't be noticable as computations are invariant on which line we choose. |