code: def test_fit_mapping(fit):
      # test Fit's `dict`-like functionality
      params = [param for param in fit]
      assert params == ["y"]
      assert params == list(fit.keys())
      assert fit["y"].mean() == list(fit.values()).pop().mean()
      key, value = list(fit.items()).pop()
      assert key == "y"
      assert value.mean() == fit["y"].mean()
  
file_path: pystan/tests/test_fit_basic_scalar.py
imports: import numpy
  import pytest
  import stan
label_desc: Use image node_id 5 for calling a global function with example usage: test_fit_mapping(fit) without return types