use G'.edgeSet \ G.edgeSet
case mp
V : Type u_1
G G' : Digraph V
h : G ≤ G'
⊢ ∃ s, s ⊆ edgeSet G' ∧ G = deleteEdges G' s
case mp
V : Type u_1
G G' : Digraph V
h : G ≤ G'
⊢ edgeSet G' \ edgeSet G ⊆ edgeSet G' ∧ G = deleteEdges G' (edgeSet G' \ edgeSet G)