def METHOD_NAME(self):
    # Setup
    load_a_id = 'load_a'
    ets_a_id = 'ets_a'
    coupling_id = 'coupling_a'
    load_ets_coupling = mock_coupling_factory(coupling_id, load_a_id, ets_a_id)
    couplings = [
        load_ets_coupling,
    ]
    diagram_commands_by_id = {
        load_a_id: [DiagramTransformation(
            model_name='some_load',
            model_type='load',
        )],
        ets_a_id: [DiagramTransformation(
            model_name='some_ets',
            model_type='ets',
        )],
        # also create a transformation which is coupling specific (ie defined in a coupling template file)
        coupling_id: [DiagramTransformation(
            model_name='some_real_expression',
            model_type='real_expression',
        )]
    }
    # Act
    diagram_graph = Diagram._diagram_commands_to_graph(
        diagram_commands_by_id,
        couplings
    )
    # Assert
    expected_diagram_graph = {
        load_a_id: {
            'some_load': DiagramNode(load_a_id, 'some_load', 'load')
        },
        ets_a_id: {
            'some_ets': DiagramNode(ets_a_id, 'some_ets', 'ets')
        },
        coupling_id: {
            'some_real_expression': DiagramNode(coupling_id, 'some_real_expression', 'real_expression')
        }
    }
    self.assertDictEqual(
        expected_diagram_graph,
        diagram_graph
    )