code: def test_json_null_literal(buffer):
      df = cudf.read_json(buffer, lines=True, engine="cudf_legacy")
  
      # first column contains a null field, type should be set to float
      # second column contains only empty fields, type should be set to int8
      np.testing.assert_array_equal(df.dtypes, ["float64", "int8"])
      np.testing.assert_array_equal(
          df["0"].to_numpy(na_value=np.nan), [1.0, np.nan]
      )
      np.testing.assert_array_equal(
          df["1"].to_numpy(na_value=0), [0, 0]
      )
  
imports: import copy
  import gzip
  import itertools
  import os
  from io import BytesIO, StringIO
  from pathlib import Path
  import numpy
  import pandas
  import pyarrow
  import pytest
  import cudf
  from cudf.testing._utils import DATETIME_TYPES, NUMERIC_TYPES, TIMEDELTA_TYPES, assert_eq
label_desc: Use image node_id 21 for calling a global function with example usage: test_json_null_literal(buffer) without return types