class_docstr: Useful commands
  - run all tests: pytest examples/orderbook_data/example.py
  - run a single test:  pytest -s --pdb --disable-warnings examples/orderbook_data/example.py::TestClass::test_basic01
class_docstr_tok: ["Useful","commands","-","run","all","tests",":","pytest","examples\/orderbook_data\/example.py","-","run","a","single","test",":","pytest","-s","--","pdb","--","disable-warnings","examples\/orderbook_data\/example.py",":",":TestClass",":",":test_basic01"]
code: def test_exp_09_trans(self):
      exprs = [
          f'TResample(Div(Sub(TResample({self.expr7_3_init("C", "Gt", "3")}, "3s", "last"), Ref(TResample({self.expr7_3_init("C", "Gt", "3")}, "3s","last"), 1)), 3), "1min", "mean")',
          f'TResample(Div(Sub(TResample({self.expr7_3_init("C", "Lt", "3")}, "3s", "last"), Ref(TResample({self.expr7_3_init("C", "Lt", "3")}, "3s","last"), 1)), 3), "1min", "mean")',
      ]
      names = ["ca_diff_intensity_3s_3s", "cb_diff_intensity_3s_3s"]
      df = D.features(
          self.stocks_list, fields=exprs, freq="transaction"
      )
      df.columns = names
      print(df)
  
imports: from arctic.arctic import Arctic
  import qlib
  from qlib.data import D
  import unittest
label_desc: Use image node_id 20 for calling the TestClass obj's underlying member method code with example usage: obj.test_exp_09_trans() without return types