`exception DotError of string`
`class type ['vertex, 'edge, 'cluster] abstract_model = object ... end`

Immutable graph model. Layout accessors, iterators and membership functions.

`module Make (G : Graphviz.GraphWithDotAttrs) : sig ... end`

This functor creates a model from a graph

`module DotG : Sig.G with type V.label = XDot.node_layout and type E.label = XDot.edge_layout`
`type cluster = string`
`type dotg_model = (DotG.vertex, DotG.edge, cluster) abstract_model`
`val read_dot : ?cmd:string -> string -> dotg_model`

Creates a model from a dot file.

`val read_xdot : string -> dotg_model`

Creates a model from an xdot file (the layout is not recomputed)