code: def _add_bias(features):
      return np.concatenate(
          [features, np.ones([features.shape[0], 1])], axis=-1
      )
  
imports: import numpy
  from inference_gym.tools.stan import stan_model
  from inference_gym.tools.stan import util
label_desc: Use image node_id 1 for calling a global function with example usage: _add_bias(features) and returns: np