old_contents: def test_Model():
      import tensorprob as tp
      model = tp.Model()
      with model:
          pass
  
new_contents: def test_Model_creation():
      import tensorprob as tp
      model = tp.Model()
      with model:
          pass
  
  def test_Model_fit():
      import tensorprob as tp
      import numpy as np
      model = tp.Model()
      with model:
          mu = tp.Scalar()
          sigma = tp.Scalar()
          X = tp.Normal(mu, sigma)
  
      model.observed(X)
      model.assign({mu: 2, sigma: 2})
      np.random.seed(0)
      data = np.random.normal(0, 1, 100)
      results = model.fit(data)
      assert results.success
  
subject: Add test for model.fit