docstr: Also test nans of differing values/construction.
docstr_tok: ["Also","test","nans","of","differing","values\/construction","."]
code: def _test_differing_nans(self):
      """
      Also test nans of differing values/construction.
      """
      sid = 1
      last_date = self.writer.last_date_in_output_for_sid(sid)
      self.assertIs(last_date, NaT)
  
      self.writer.pad(sid, TEST_CALENDAR_START)
  
      last_date = self.writer.last_date_in_output_for_sid(sid)
      self.assertEqual(last_date, TEST_CALENDAR_START)
  
      freq = self.market_opens.index.freq
      minute = self.market_opens[TEST_CALENDAR_START + freq]
      minutes = date_range(minute, periods=9, freq="min")
      data = DataFrame(
          data={
              "open": (
                  (0b11111111111 << 52) + arange(1, 10, dtype=int64)
              ).view(float64),
              "high": (
                  (0b11111111111 << 52) + arange(11, 20, dtype=int64)
              ).view(float64),
              "low": (
                  (0b11111111111 << 52) + arange(21, 30, dtype=int64)
              ).view(float64),
              "close": (
                  (0b11111111111 << 52) + arange(31, 40, dtype=int64)
              ).view(float64),
              "volume": full(9, 0.0),
          },
          index=[minutes],
      )
      self.writer.write_sid(sid, data)
  
      fields = ["open", "high", "low", "close", "volume"]
  
      ohlcv_window = list(
          map(
              transpose,
              self.reader.load_raw_arrays(
                  fields,
                  minutes[0],
                  minutes[-1],
                  [sid],
              ),
          )
      )
  
      for i, field in enumerate(fields):
          if field != "volume":
              assert_array_equal(full(9, nan), ohlcv_window[i][0])
          else:
              assert_array_equal(zeros(9), ohlcv_window[i][0])
  
imports: from datetime import timedelta
  import os
  from numpy import arange, array, int64, float64, full, nan, transpose, zeros
  from numpy.testing import assert_almost_equal, assert_array_equal
  from pandas import DataFrame, DatetimeIndex, Timestamp, Timedelta, NaT, date_range
  from catalyst.data.minute_bars import BcolzMinuteBarMetadata, BcolzMinuteOverlappingData, US_EQUITIES_MINUTES_PER_DAY, BcolzMinuteWriterColumnMismatch, H5MinuteBarUpdateWriter, H5MinuteBarUpdateReader
  from catalyst.exchange.exchange_bcolz import BcolzExchangeBarWriter, BcolzExchangeBarReader
  from catalyst.testing.fixtures import WithAssetFinder, WithInstanceTmpDir, WithTradingCalendars, CatalystTestCase
label_desc: Use image node_id 16 for calling the BcolzMinuteBarTestCase obj's underlying member method code with example usage: obj._test_differing_nans() without return types