docstr: edges added with unknown origin should be labelled as unknown origin
docstr_tok: ["edges","added","with","unknown","origin","should","be","labelled","as","unknown","origin"]
code: def test_add_weighted_edges_from_unknown(self):
      """edges added with unknown origin should be labelled as unknown origin"""
  
      sm = StructureModel()
      edges = [(1, 2, 0.5), (2, 3, 0.5)]
      sm.add_weighted_edges_from(edges, origin="unknown")
  
      assert all(
          (u, v, w) in sm.edges.data("weight") for u, v, w in edges
      )
      assert all(
          (u, v, "unknown") in sm.edges.data("origin")
          for u, v, w in edges
      )
  
imports: import pytest
  from networkx.exception import NodeNotFound
  from causalnex.structure import StructureModel
label_desc: Use image node_id 2 for calling the TestStructureModelAddWeightedEdgesFrom obj's underlying member method code with example usage: obj.test_add_weighted_edges_from_unknown() without return types