code: def _is_null(r: Any):
      pd = _lazy_import_pandas()
      if pd:
          return pd.isnull(r)
      try:
          return np.isnan(r)
      except TypeError:
          return r is None
  
file_path: ray/python/ray/data/_internal/null_aggregate.py
imports: from types import ModuleType
  from typing import Any, Callable, Tuple, Union
  import numpy
  from ray.data.block import AggType, Block, KeyType, T, U
label_desc: Use image node_id 9 for calling a global function with example usage: _is_null(r) and returns: pd, np, unknown