code: def test_get_adjustments(self, data_frequency, field):
      asset = self.asset_finder.retrieve_asset(self.DIVIDEND_ASSET_SID)
      calendar = self.trading_calendars[Equity]
      day = calendar.day
      dividend_date = self.trading_days[2]
  
      prev_day_price = 1.006
      dividend_amount = 0.5  # see self.make_dividends_data
      ratio = 1.0 - dividend_amount / prev_day_price
  
      cases = OrderedDict(
          [
              ((dividend_date - day, dividend_date - day), 1.0),
              ((dividend_date - day, dividend_date), ratio),
              ((dividend_date - day, dividend_date + day), ratio),
              ((dividend_date, dividend_date), 1.0),
              ((dividend_date, dividend_date + day), 1.0),
              ((dividend_date + day, dividend_date + day), 1.0),
          ]
      )
  
      for (dt, perspective_dt), expected in iteritems(cases):
          if data_frequency == "minute":
              dt = calendar.session_open(dt)
              perspective_dt = calendar.session_open(perspective_dt)
  
          val = self.data_portal.get_adjustments(
              asset,
              field,
              dt,
              perspective_dt,
          )[0]
          assert_almost_equal(
              val,
              expected,
              err_msg="at dt={} perspective={}".format(
                  dt, perspective_dt
              ),
          )
  
imports: from collections import OrderedDict
  from numpy import array, append, nan, full
  from numpy.testing import assert_almost_equal
  import pandas
  from pandas import Timedelta
  from six import iteritems
  from zipline.assets import Equity, Future
  from zipline.data.data_portal import HISTORY_FREQUENCIES, OHLCV_FIELDS
  from zipline.data.minute_bars import FUTURES_MINUTES_PER_DAY, US_EQUITIES_MINUTES_PER_DAY
  from zipline.testing import parameter_space
  from zipline.testing.fixtures import ZiplineTestCase, WithTradingSessions, WithDataPortal, alias
  from zipline.testing.predicates import assert_equal
  from zipline.utils.numpy_utils import float64_dtype
label_desc: Use image node_id 12 for calling the DataPortalTestBase obj's underlying member method code with example usage: obj.test_get_adjustments(data_frequency, field) without return types