docstr: it should be possible to add edges with custom attributes
docstr_tok: ["it","should","be","possible","to","add","edges","with","custom","attributes"]
code: def test_add_edges_from_custom_attr(self):
      """it should be possible to add edges with custom attributes"""
  
      sm = StructureModel()
      edges = [(1, 2), (2, 3)]
      sm.add_edges_from(edges, x="Y")
  
      assert all(edge in sm.edges for edge in edges)
      assert all((u, v, "Y") in sm.edges.data("x") for u, v in edges)
  
imports: import pytest
  from networkx.exception import NodeNotFound
  from causalnex.structure import StructureModel
label_desc: Use image node_id 6 for calling the TestStructureModelAddEdgesFrom obj's underlying member method code with example usage: obj.test_add_edges_from_custom_attr() without return types