GdaGraph Data model to keep graphs' layout An instance of this object is required for each unique graph that is to be created. It is the "model" part of the graph. The "view" and "controler" parts are brought by the #GnomeDbCanvas and associated widgets. The graph can be "attached" to a specific #GdaObject object using the "ref_object" property. If the referenced object is destroyed, then the graph object will also automaticallu be destroyed. @object: @priv: @dict: @type: @Returns: @graph: @Returns: @graph: @Returns: @graph: @ref_obj: @create_if_needed: @Returns: @graph: @item: @graph: @item: