code: def test_add_field_v2(self):
      ds = DataSet({"x": [3, 4]})
      ds.add_field(
          "y", [["hello", "world"], ["this", "is", "a", "test"]]
      )
      # ds.apply(lambda x:[x['x']]*3, new_field_name='y')
      print(ds)
  
imports: import os
  import pytest
  import numpy
  from fastNLP.core.dataset import DataSet, FieldArray, Instance, ApplyResultException
  from fastNLP import logger
label_desc: Use image node_id 23 for calling the TestDataSetMethods obj's underlying member method code with example usage: obj.test_add_field_v2() without return types