code: def setUp(self):
      self.phi1 = DiscreteFactor(
          ["x1", "x2", "x3"], [2, 3, 2], range(12)
      )
      self.phi2 = DiscreteFactor(
          ["x3", "x4", "x1"], [2, 2, 2], range(8)
      )
      self.phi3 = DiscreteFactor(
          ["x5", "x6", "x7"], [2, 2, 2], range(8)
      )
      self.phi4 = DiscreteFactor(
          ["x5", "x7", "x8"], [2, 2, 2], range(8)
      )
  
file_path: pgmpy/pgmpy/tests/test_factors/test_FactorSet.py
imports: import unittest
  from pgmpy.factors import FactorSet
  from pgmpy.factors.discrete import DiscreteFactor
label_desc: Use image node_id 1 for calling the TestFactorSet obj's underlying member method code with example usage: obj.setUp() without return types