# Append the JSON representation of the relationship to the specified buffer.
	#
	# Use the IDs specfied by `graph.nodes`.
	redef fun append_json_for(graph, v) do
		v.stream.write "\{\"type\":"
		rel_type.as(not null).serialize_to(v)
		v.stream.write ",\"properties\":"
		properties.serialize_to(v)
		v.stream.write ",\"from\":"
		graph.nodes.id_of(from).serialize_to(v)
		v.stream.write ",\"to\":"
		graph.nodes.id_of(to).serialize_to(v)
		v.stream.write "}"
	end

	# Append the JSON representation of the node to the specified buffer.
	redef fun append_json_for(graph, v) do
		accept_json_serializer v
	end