code: def convection_lorenz_bridge_unknown_scales():
      """Lorenz System with observed convection and missing observations.
  
      Returns:
        target: StanModel.
      """
      dataset = data.convection_lorenz_bridge()
      del dataset["innovation_scale"]
      del dataset["observation_scale"]
      return (
          lorenz_system.partially_observed_lorenz_system_unknown_scales(
              **dataset
          )
      )
  
imports: from inference_gym.internal import data
  from inference_gym.tools.stan import brownian_motion
  from inference_gym.tools.stan import eight_schools
  from inference_gym.tools.stan import item_response_theory
  from inference_gym.tools.stan import log_gaussian_cox_process
  from inference_gym.tools.stan import logistic_regression
  from inference_gym.tools.stan import lorenz_system
  from inference_gym.tools.stan import probit_regression
  from inference_gym.tools.stan import radon_contextual_effects
  from inference_gym.tools.stan import radon_contextual_effects_halfnormal
  from inference_gym.tools.stan import sparse_logistic_regression
  from inference_gym.tools.stan import stochastic_volatility
label_desc: Use image node_id 4 for calling a global function with example usage: convection_lorenz_bridge_unknown_scales() and returns: lorenz_system