code: def test_sum_receives_no_values():
      component = Sum()
      results = component.run(values=[])
      assert results == {"total": 0}
  
imports: from haystack.testing.sample_components import Sum
  from haystack.core.serialization import component_to_dict, component_from_dict
label_desc: Use image node_id 1 for calling a global function with example usage: test_sum_receives_no_values() without return types