code: def test_is_valid_adjustment_set(self):
      self.assertTrue(
          self.infer.is_valid_adjustment_set(
              X=["x1", "x2"],
              Y=["y1", "y2"],
              adjustment_set=["z1", "z2"],
          )
      )
  
      self.assertFalse(
          self.infer.is_valid_adjustment_set(
              X=["x1", "x2"], Y=["y1", "y2"], adjustment_set=["z1"]
          )
      )
  
      self.assertTrue(
          self.infer.is_valid_adjustment_set(
              X=["x1", "x2"], Y=["y1", "y2"], adjustment_set=["z2"]
          )
      )
  
imports: import unittest
  import numpy
  import numpy.testing
  import pandas
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.inference.CausalInference import CausalInference
  from pgmpy.models import BayesianNetwork
label_desc: Use image node_id 4 for calling the TestAdjustmentSet obj's underlying member method code with example usage: obj.test_is_valid_adjustment_set() without return types