code: def ensure_treasury_data(
      symbol, first_date, last_date, now, environ=None
  ):
      """
      Ensure we have treasury data from treasury module associated with
      `symbol`.
  
      Parameters
      ----------
      symbol : str
          Benchmark symbol for which we're loading associated treasury curves.
      first_date : pd.Timestamp
          First date required to be in the cache.
      last_date : pd.Timestamp
          Last date required to be in the cache.
      now : pd.Timestamp
          The current time.  This is used to prevent repeated attempts to
          re-download data that isn't available due to scheduling quirks or other
          failures.
  
      We attempt to download data unless we already have data stored in the cache
      for `module_name` whose first entry is before or on `first_date` and whose
      last entry is on or after `last_date`.
  
      If we perform a download and the cache criteria are not satisfied, we wait
      at least one hour before attempting a redownload.  This is determined by
      comparing the current time to the result of os.path.getmtime on the cache
      path.
      """
      loader_module, filename, source = INDEX_MAPPING.get(
          symbol,
          INDEX_MAPPING["SPY"],
      )
      first_date = max(
          first_date, loader_module.earliest_possible_date()
      )
  
      data = _load_cached_data(
          filename, first_date, last_date, now, "treasury", environ
      )
      if data is not None:
          return data
  
      # If no cached data was found or it was missing any dates then download the
      # necessary data.
      logger.info(
          "Downloading treasury data for {symbol!r}.", symbol=symbol
      )
  
      try:
          data = loader_module.get_treasury_data(first_date, last_date)
          data.to_csv(get_data_filepath(filename, environ))
      except (OSError, IOError, HTTPError):
          logger.exception("failed to cache treasury data")
      if not has_data_for_dates(data, first_date, last_date):
          logger.warn(
              "Still don't have expected data after redownload!"
          )
      return data
  
imports: import os
  from collections import OrderedDict
  import logbook
  import pandas
  import pytz
  from pandas_datareader.data import DataReader
  from six import iteritems
  from six.moves.urllib_error import HTTPError
  from catalyst.constants import LOG_LEVEL
  from catalyst.utils.calendars import get_calendar
  from .None import treasuries, treasuries_can
  from .benchmarks import get_benchmark_returns
  from ..utils.deprecate import deprecated
  from ..utils.paths import cache_root, data_root
label_desc: Use image node_id 10 for calling a global function with example usage: ensure_treasury_data(symbol, first_date, last_date, now, environ) and returns: data, data