Graph Identity  The empty graph

(Monad (MaybeT g), Eq (Vertex (MaybeT g)), Eq (Edge (MaybeT g)), Graph g) => Graph (MaybeT g)  
(Monad (IdentityT g), Eq (Vertex (IdentityT g)), Eq (Edge (IdentityT g)), Graph g) => Graph (IdentityT g)  
(Monad (Dual g), Eq (Vertex (Dual g)), Eq (Edge (Dual g)), Graph g) => Graph (Dual g)  
(Monad (AdjacencyList i), Eq (Vertex (AdjacencyList i)), Eq (Edge (AdjacencyList i)), Ord i) => Graph (AdjacencyList i)  
(Monad (WriterT m g), Eq (Vertex (WriterT m g)), Eq (Edge (WriterT m g)), Graph g, Monoid m) => Graph (WriterT m g)  
(Monad (WriterT m g), Eq (Vertex (WriterT m g)), Eq (Edge (WriterT m g)), Graph g, Monoid m) => Graph (WriterT m g)  
(Monad (StateT s g), Eq (Vertex (StateT s g)), Eq (Edge (StateT s g)), Graph g) => Graph (StateT s g)  
(Monad (StateT s g), Eq (Vertex (StateT s g)), Eq (Edge (StateT s g)), Graph g) => Graph (StateT s g)  
(Monad (ReaderT m g), Eq (Vertex (ReaderT m g)), Eq (Edge (ReaderT m g)), Graph g) => Graph (ReaderT m g)  
(Monad (ErrorT e g), Eq (Vertex (ErrorT e g)), Eq (Edge (ErrorT e g)), Graph g, Error e) => Graph (ErrorT e g)  
(Monad (AdjacencyMatrix arr i), Eq (Vertex (AdjacencyMatrix arr i)), Eq (Edge (AdjacencyMatrix arr i)), Ord i) => Graph (AdjacencyMatrix arr i)  
(Monad (RWST r w s g), Eq (Vertex (RWST r w s g)), Eq (Edge (RWST r w s g)), Graph g, Monoid w) => Graph (RWST r w s g)  
(Monad (RWST r w s g), Eq (Vertex (RWST r w s g)), Eq (Edge (RWST r w s g)), Graph g, Monoid w) => Graph (RWST r w s g)  