code: def test_check_instances_dict_formatting():
      """[Utils] check_instances: test formatting of dict."""
      instances = {
          "a": [OLS(), ("ols", OLS()), ("ols", OLS()), ["list", OLS()]],
          "b": [],
          "c": [OLS(), ("ols", OLS())],
      }
  
      formatted = _check_instances(instances)
  
      for k, v in formatted.items():
          if k == "b":
              assert len(v) == 0
          else:
              for i in v:
                  strings = []
                  assert isinstance(i, tuple)
                  assert isinstance(i[0], str)
                  assert isinstance(i[1], OLS)
                  assert i[0] not in strings
                  strings.append(i[0])
  
file_path: mlens/mlens/utils/tests/test_formatting.py
imports: from mlens.utils.dummy import OLS
  from mlens.utils.formatting import _check_format, _assert_format, _format_instances, _check_instances
label_desc: Use image node_id 15 for calling a global function with example usage: test_check_instances_dict_formatting() without return types