code: def _is_primitive(x):
      """Returns True if x is a primitive type.
  
      Primitive types are int, float, str, bool, and None.
      """
      return isinstance(x, (int, float, str, bool)) or x is None
  
file_path: ray/python/ray/tune/impl/placeholder.py
imports: from collections import defaultdict
  import hashlib
  from typing import Any, Dict, Tuple
  from ray.tune.search.sample import Categorical, Domain, Function
  from ray.tune.search.variant_generator import assign_value
  from ray.util.annotations import DeveloperAPI
label_desc: Use image node_id 3 for calling a global function with example usage: _is_primitive(x) and returns: unknown