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_07_1(self):
      # NOTE: based on transaction frequency (i.e. freq="transaction")
      expr7_3 = (
          lambda funccode, code, time_interval: f"TResample(Rolling(Eq($function_code,  {ord(funccode)}) & {code}($ask_order, $bid_order) , '{time_interval}s', 'sum')   / Rolling($function_code, '{time_interval}s', 'count') , '1min', 'mean')"
      )
  
      exprs = [expr7_3("C", "Gt", "3"), expr7_3("C", "Lt", "3")]
      names = ["ca_intensity_3s", "cb_intensity_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 15 for calling the TestClass obj's underlying member method code with example usage: obj.test_exp_07_1() without return types