docstr: adding an edge again should update the edges origin attr
docstr_tok: ["adding","an","edge","again","should","update","the","edges","origin","attr"]
code: def test_add_edge_multiple_times(self):
      """adding an edge again should update the edges origin attr"""
  
      sm = StructureModel()
      sm.add_edge(1, 2, origin="unknown")
      assert (1, 2, "unknown") in sm.edges.data("origin")
      sm.add_edge(1, 2, origin="learned")
      assert (1, 2, "learned") in sm.edges.data("origin")
  
imports: import pytest
  from networkx.exception import NodeNotFound
  from causalnex.structure import StructureModel
label_desc: Use image node_id 7 for calling the TestStructureModelAddEdge obj's underlying member method code with example usage: obj.test_add_edge_multiple_times() without return types