code: def test_null_singleton():
      with pytest.raises(RuntimeError):
          pa.NullScalar()
  
imports: import datetime
  import decimal
  import pytest
  import sys
  import weakref
  import numpy
  import pyarrow
  import pyarrow.compute
  from pyarrow.tests import util
label_desc: Use image node_id 3 for calling a global function with example usage: test_null_singleton() without return types