code: def test_factor_add_sub():
      # Test adding and subtracting Factors
      f1 = F.Factor("t", [2, 3, 4])
      f2 = F.Factor("t", [2, 3])
      # Terms do not cancel in addition
      assert f1 + f2 == F.Formula(np.hstack((f1.terms, f2.terms)))
      assert f1 - f2 == F.Factor("t", [4])
      f3 = F.Factor("p", [0, 1])
      assert f1 + f3 == F.Formula(np.hstack((f1.terms, f3.terms)))
      assert f1 - f3 == f1
  
imports: from warnings import catch_warnings, simplefilter
  import numpy
  import pytest
  import sympy
  from numpy.core.records import fromrecords
  from numpy.testing import assert_almost_equal, assert_array_equal
  from sympy.utilities.lambdify import implemented_function
  from nipy.utils import VisibleDeprecationWarning
  from ..None import formulae
  from ..formulae import Term, terms
label_desc: Use image node_id 10 for calling a global function with example usage: test_factor_add_sub() without return types