code: def setUp(self) -> None:
      self.instrument = "0050"
      self.start_time = "2022-01-01"
      self.end_time = "2022-02-01"
      self.freq = "day"
      self.mock_df = MOCK_DF[MOCK_DF["symbol"] == self.instrument]
  
file_path: qlib/tests/ops/test_elem_operator.py
imports: import unittest
  import numpy
  import pytest
  from qlib.data import DatasetProvider
  from qlib.data.data import ExpressionD
  from qlib.tests import TestOperatorData, TestMockData, MOCK_DF
  from qlib.config import C
label_desc: Use image node_id 1 for calling the TestElementOperator obj's underlying member method code with example usage: obj.setUp() without return types