The method to go from json to placement (currently usused) was wrong.
placement_from_json
It tried to get a vertex from a graph but placements need a MachineVertex and we no longer have a machine Graph.
So removed the option to load a vertex from the graph.
The method to go from json to placement (currently usused) was wrong. placement_from_json
It tried to get a vertex from a graph but placements need a MachineVertex and we no longer have a machine Graph. So removed the option to load a vertex from the graph.
The rest of the changes are typing and testing