code: def test_log_prob(posterior, x: float, y: float):
      constrained_params = posterior.constrain_pars([x, y])
      constrained_pars = {
          "x": constrained_params[0],
          "y": constrained_params[1],
          "x_mult": constrained_params[2],
          "z": constrained_params[3],
      }
      unconstrained_params = posterior.unconstrain_pars(
          constrained_pars
      )
      assert np.allclose([x, y], unconstrained_params)
  
imports: import random
  import numpy
  import pytest
  import stan
label_desc: Use image node_id 2 for calling a global function with example usage: test_log_prob(posterior, x, y) without return types