code: def test_add_edge():
      m1 = Categorical([[0.5, 0.5]])
      m2 = Categorical([[0.5, 0.5]])
  
      f1 = Categorical([[0.8, 0.1]])
      f2 = JointCategorical([[[0.2, 0.1], [0.1, 0.6]]])
  
      model = FactorGraph([f1, f2], [m1, m2])
      assert model._factor_edges == [[], []]
      assert model._marginal_edges == [[], []]
  
      model.add_edge(m1, f1)
      assert model._factor_edges == [[0], []]
      assert model._marginal_edges == [[0], []]
  
      model.add_edge(m1, f2)
      assert model._factor_edges == [[0], [0]]
      assert model._marginal_edges == [[0, 1], []]
  
      model.add_edge(m2, f2)
      assert model._factor_edges == [[0], [0, 1]]
      assert model._marginal_edges == [[0, 1], [1]]
  
imports: import numpy
  import torch
  import pytest
  from pomegranate.factor_graph import FactorGraph
  from pomegranate.distributions import Exponential
  from pomegranate.distributions import Categorical
  from pomegranate.distributions import JointCategorical
  from nose.tools import assert_raises
  from numpy.testing import assert_array_almost_equal
label_desc: Use image node_id 12 for calling a global function with example usage: test_add_edge() without return types