code: def test_delete_field(self):
      dd = DataSet()
      dd.add_field("x", [[1, 2, 3]] * 10)
      dd.add_field("y", [[1, 2, 3, 4]] * 10)
      dd.delete_field("x")
      assert ("x" in dd.field_arrays) == False
      assert "y" in dd.field_arrays
  
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 3 for calling the TestDataSetMethods obj's underlying member method code with example usage: obj.test_delete_field() without return types