docstr: Creating a StructureModel using constructor should give all edges unknown origin
docstr_tok: ["Creating","a","StructureModel","using","constructor","should","give","all","edges","unknown","origin"]
code: def test_init_has_origin(self):
      """Creating a StructureModel using constructor should give all edges unknown origin"""
  
      sm = StructureModel([(1, 2)])
      assert (1, 2) in sm.edges
      assert (1, 2, "unknown") in sm.edges.data("origin")
  
imports: import pytest
  from networkx.exception import NodeNotFound
  from causalnex.structure import StructureModel
label_desc: Use image node_id 1 for calling the TestStructureModel obj's underlying member method code with example usage: obj.test_init_has_origin() without return types