code: def _to_list(obj):
      """Put obj in list if it is not a list."""
      if not isinstance(obj, list):
          return [obj]
      else:
          return obj
  
file_path: sktime/sktime/registry/tests/test_lookup.py
imports: import pytest
  from sktime.base import BaseObject
  from sktime.registry import all_estimators, all_tags, scitype
  from sktime.registry._base_classes import BASE_CLASS_LOOKUP, BASE_CLASS_SCITYPE_LIST, TRANSFORMER_MIXIN_SCITYPE_LIST
  from sktime.registry._lookup import _check_estimator_types
label_desc: Use image node_id 1 for calling a global function with example usage: _to_list(obj) and returns: list, obj