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_06(self):
      t = 3
      expr6_price_func = (
          lambda name, index, method: f'2 * (TResample(${name}{index}, "{t}s", "{method}") - Ref(TResample(${name}{index}, "{t}s", "{method}"), 1)) / {t}'
      )
      exprs = []
      names = []
      for i in range(1, 11):
          for name in ["bid", "ask"]:
              exprs.append(
                  f"TResample({expr6_price_func(name, i, 'last')}, '1min', 'mean') / {self.expr_sum_buy_ask_1}"
              )
              names.append(f"p_diff_{name}{i}_{t}s")
  
      for i in range(1, 11):
          for name in ["asize", "bsize"]:
              exprs.append(
                  f"TResample({expr6_price_func(name, i, 'mean')}, '1min', 'mean') / {self.total_volume}"
              )
              names.append(f"v_diff_{name}{i}_{t}s")
  
      df = D.features(self.stocks_list, fields=exprs, freq="ticks")
      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 13 for calling the TestClass obj's underlying member method code with example usage: obj.test_exp_06() without return types