docstr: The subgraph returned should still be a StructureModel instance
docstr_tok: ["The","subgraph","returned","should","still","be","a","StructureModel","instance"]
code: def test_instance_type(self):
      """The subgraph returned should still be a StructureModel instance"""
  
      sm = StructureModel()
      sm.add_edges_from([(0, 1), (1, 2), (1, 3), (4, 6)])
      subgraph = sm.get_markov_blanket(2)
  
      assert isinstance(subgraph, StructureModel)
  
imports: import pytest
  from networkx.exception import NodeNotFound
  from causalnex.structure import StructureModel
label_desc: Use image node_id 7 for calling the TestStructureModelGetMarkovBlanket obj's underlying member method code with example usage: obj.test_instance_type() without return types