code: def fit(posterior):
      assert posterior is not None
      return posterior.sample(
          num_samples=num_samples, num_chains=num_chains
      )
  
file_path: pystan/tests/test_fit_basic_scalar.py
imports: import numpy
  import pytest
  import stan
label_desc: Use image node_id 2 for calling a global function with example usage: fit(posterior) and returns: posterior