code: def test_factorset_add_remove_factors(self):
      self.factor_set1 = FactorSet()
      self.factor_set1.add_factors(self.phi1, self.phi2)
      self.assertEqual(
          {self.phi1, self.phi2}, self.factor_set1.get_factors()
      )
      self.factor_set1.remove_factors(self.phi2)
      self.assertEqual({self.phi1}, self.factor_set1.get_factors())
  
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 3 for calling the TestFactorSet obj's underlying member method code with example usage: obj.test_factorset_add_remove_factors() without return types