new_contents: 
  import numpy as np
  from tensorprob import Model, Uniform, Normal, Mix2
  
  def test_mix2():
      with Model() as model:
          mu1 = Uniform()
          mu2 = Uniform()
          sigma1 = Uniform(lower=0)
          sigma2 = Uniform(lower=0)
          f = Uniform(lower=0, upper=1)
  
          X = Mix2(
              f,
              Normal(mu1, sigma1),
              Normal(mu2, sigma2),
          )
      model.observed(X)
      model.initialize({
          f: 0.5,
          mu1: -1,
          mu2: 1,
          sigma1: 1,
          sigma2: 2,
      })
      model.fit([1,2,3])
  
subject: Test Mix2