code: def _test_calculate_impact_sell(self):
      answer_key = [
          # We ordered -10 contracts, but are capped at -(100 * 0.05) = -5
          (91485.499914831875, -5),
          (91486.499914830943, -5),
          (None, None),
      ]
      order = Order(
          dt=pd.Timestamp.now(tz="utc").round("min"),
          asset=self.ASSET,
          amount=-10,
      )
      self._calculate_impact(order, answer_key)
  
imports: from collections import namedtuple
  import datetime
  from math import sqrt
  from nose_parameterized import parameterized
  from pandas.tslib import normalize_date
  import numpy
  import pandas
  import pytz
  from catalyst.assets import Equity, Future
  from catalyst.data.data_portal import DataPortal
  from catalyst.finance.asset_restrictions import NoRestrictions
  from catalyst.finance.order import Order
  from catalyst.finance.slippage import EquitySlippageModel, fill_price_worse_than_limit_price, FutureSlippageModel, SlippageModel, VolatilityVolumeShare, VolumeShareSlippage
  from catalyst.protocol import DATASOURCE_TYPE, BarData
  from catalyst.testing import create_minute_bar_data, tmp_bcolz_equity_minute_bar_reader
  from catalyst.testing.fixtures import WithCreateBarData, WithDataPortal, WithSimParams, WithTradingEnvironment, CatalystTestCase
  from catalyst.utils.classproperty import classproperty
label_desc: Use image node_id 5 for calling the VolatilityVolumeShareTestCase obj's underlying member method code with example usage: obj._test_calculate_impact_sell() without return types