docstr: Test that we can write an empty country to an HDF5 daily bar writer.
  
  This is useful functionality for some tests, but it requires a bunch of
  special cased logic in the writer.
code: def test_write_empty_country(self):
      """
      Test that we can write an empty country to an HDF5 daily bar writer.
  
      This is useful functionality for some tests, but it requires a bunch of
      special cased logic in the writer.
      """
      path = self.tmpdir.getpath("empty.h5")
      writer = HDF5DailyBarWriter(path, date_chunk_size=30)
      writer.write_from_sid_df_pairs("US", iter(()))
  
      reader = HDF5DailyBarReader.from_path(path, "US")
  
      assert_equal(reader.sids, np.array([], dtype="int64"))
  
      empty_dates = np.array([], dtype="datetime64[ns]")
      assert_equal(reader.asset_start_dates, empty_dates)
      assert_equal(reader.asset_end_dates, empty_dates)
      assert_equal(reader.dates, empty_dates)
  
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 1 for calling the H5WriterTestCase obj's underlying member method code with example usage: obj.test_write_empty_country() without return types