constructor
case mp
V : Type u_1
G G' : Digraph V
h : G < G'
⊢ Set.Nonempty (edgeSet G' \ edgeSet G) ∧
    edgeSet G' \ edgeSet G ⊆ edgeSet G' ∧ G = deleteEdges G' (edgeSet G' \ edgeSet G)
case mp.left
V : Type u_1
G G' : Digraph V
h : G < G'
⊢ Set.Nonempty (edgeSet G' \ edgeSet G)

case mp.right
V : Type u_1
G G' : Digraph V
h : G < G'
⊢ edgeSet G' \ edgeSet G ⊆ edgeSet G' ∧ G = deleteEdges G' (edgeSet G' \ edgeSet G)