Backend.Slicetype t = sliceval t : t Irmin__.Type.ttype contents = Contents.hash * Contents.valueval contents_t : contents Irmin__.Type.ttype node = Node.hash * Node.valueval node_t : node Irmin__.Type.ttype commit = Commit.hash * Commit.valueval commit_t : commit Irmin__.Type.tval value_t : value Irmin__.Type.tval empty : unit -> t Lwt.t