code: def test_regiter_custom_ops(self):
      instruments = ["SH600000"]
      fields = ["Diff($close)", "Distance($close, Ref($close, 1))"]
      print(
          D.features(
              instruments,
              fields,
              start_time="2010-01-01",
              end_time="2017-12-31",
              freq="day",
          )
      )
  
file_path: qlib/tests/test_register_ops.py
imports: import unittest
  import numpy
  from qlib.data import D
  from qlib.data.ops import ElemOperator, PairOperator
  from qlib.tests import TestAutoData
label_desc: Use image node_id 2 for calling the TestRegiterCustomOps obj's underlying member method code with example usage: obj.test_regiter_custom_ops() without return types