code: def test_unlimit(self):
      # fields = ["P(Mean($$roewa_q, 1))", "P($$roewa_q)", "P(Mean($$roewa_q, 2))", "P(Ref($$roewa_q, 1))", "P((Ref($$roewa_q, 1) +$$roewa_q) / 2)"]
      fields = ["P($$roewa_q)"]
      instruments = ["sh600519"]
      _ = D.features(
          instruments, fields, freq="day"
      )  # this should not raise error
      data = D.features(
          instruments, fields, end_time="2020-01-01", freq="day"
      )  # this should not raise error
      s = data.iloc[:, 0]
      # You can check the expected value based on the content in `docs/advanced/PIT.rst`
      expect = """
          instrument  datetime
          sh600519    2005-01-04         NaN
                      2007-04-30    0.090219
                      2007-08-17    0.139330
                      2007-10-23    0.245863
                      2008-03-03    0.347900
                      2008-03-13    0.395989
                      2008-04-22    0.100724
                      2008-08-28    0.249968
                      2008-10-27    0.334120
                      2009-03-25    0.390117
                      2009-04-21    0.102675
                      2009-08-07    0.230712
                      2009-10-26    0.300730
                      2010-04-02    0.335461
                      2010-04-26    0.083825
                      2010-08-12    0.200545
                      2010-10-29    0.260986
                      2011-03-21    0.307393
                      2011-04-25    0.097411
                      2011-08-31    0.248251
                      2011-10-18    0.318919
                      2012-03-23    0.403900
                      2012-04-11    0.403925
                      2012-04-26    0.112148
                      2012-08-10    0.264847
                      2012-10-26    0.370487
                      2013-03-29    0.450047
                      2013-04-18    0.099958
                      2013-09-02    0.210442
                      2013-10-16    0.304543
                      2014-03-25    0.394328
                      2014-04-25    0.083217
                      2014-08-29    0.164503
                      2014-10-30    0.234085
                      2015-04-21    0.078494
                      2015-08-28    0.137504
                      2015-10-23    0.201709
                      2016-03-24    0.264205
                      2016-04-21    0.073664
                      2016-08-29    0.136576
                      2016-10-31    0.188062
                      2017-04-17    0.244385
                      2017-04-25    0.080614
                      2017-07-28    0.151510
                      2017-10-26    0.254166
                      2018-03-28    0.329542
                      2018-05-02    0.088887
                      2018-08-02    0.170563
                      2018-10-29    0.255220
                      2019-03-29    0.344644
                      2019-04-25    0.094737
                      2019-07-15    0.000000
                      2019-07-18    0.175322
                      2019-10-16    0.255819
          Name: P($$roewa_q), dtype: float32
          """
      self.check_same(s[~s.duplicated().values], expect)
  
imports: import sys
  import qlib
  import shutil
  import unittest
  import pytest
  import pandas
  import baostock
  from pathlib import Path
  from qlib.data import D
  from qlib.tests.data import GetData
  from dump_pit import DumpPitData
  from collector import Run
label_desc: Use image node_id 9 for calling the TestPIT obj's underlying member method code with example usage: obj.test_unlimit() without return types