intro h
graph✝ : Graph
a✝² : Class graph✝
child✝¹ : Class.Child a✝²
a✝¹ : Path graph✝ (Class.Child.class child✝¹)
child✝ : Class.Child a✝²
a✝ : Path graph✝ (Class.Child.class child✝)
⊢ Path.cons child✝¹ a✝¹ ≂ Path.cons child✝ a✝ → prefix? (Path.cons child✝¹ a✝¹) = prefix? (Path.cons child✝ a✝)
graph✝ : Graph
a✝² : Class graph✝
child✝¹ : Class.Child a✝²
a✝¹ : Path graph✝ (Class.Child.class child✝¹)
child✝ : Class.Child a✝²
a✝ : Path graph✝ (Class.Child.class child✝)
h : Path.cons child✝¹ a✝¹ ≂ Path.cons child✝ a✝
⊢ prefix? (Path.cons child✝¹ a✝¹) = prefix? (Path.cons child✝ a✝)