code: def test_multi_country_attributes(self):
      path = self.tmpdir.getpath("multi.h5")
      writer = HDF5DailyBarWriter(path, date_chunk_size=30)
  
      US = pd.DataFrame(
          data=np.ones((3, 5)),
          index=pd.to_datetime(
              ["2014-01-02", "2014-01-03", "2014-01-06"]
          ),
          columns=np.arange(1, 6),
      )
  
      CA = pd.DataFrame(
          data=np.ones((2, 4)) * 2,
          index=pd.to_datetime(["2014-01-04", "2014-01-07"]),
          columns=np.arange(100, 104),
      )
  
      def ohlcv(frame):
          return {
              "open": frame,
              "high": frame,
              "low": frame,
              "close": frame,
              "volume": frame,
          }
  
      writer.write("US", ohlcv(US))
      writer.write("CA", ohlcv(CA))
  
      reader = MultiCountryDailyBarReader.from_path(path)
      assert_equal(reader.countries, {"US", "CA"})
      assert_equal(
          reader.sessions,
          pd.to_datetime(
              [
                  "2014-01-02",
                  "2014-01-03",
                  "2014-01-04",
                  "2014-01-06",
                  "2014-01-07",
              ],
              utc=True,
          ),
      )
  
file_path: zipline/tests/data/test_hdf5_daily_bars.py
imports: import numpy
  import pandas
  from zipline.data.hdf5_daily_bars import HDF5DailyBarReader, HDF5DailyBarWriter, MultiCountryDailyBarReader
  import zipline.testing.fixtures
  from zipline.testing.predicates import assert_equal
label_desc: Use image node_id 2 for calling the H5WriterTestCase obj's underlying member method code with example usage: obj.test_multi_country_attributes() and returns: dict