code: def __localize_prices_and_factor(self, prices, factor, tz):
      if tz is not None:
          factor = factor.unstack()
          factor.index = factor.index.tz_localize(tz)
          factor = factor.stack()
          prices = prices.copy()
          prices.index = prices.index.tz_localize(tz)
      return prices, factor
  
file_path: alphalens/alphalens/tests/test_tears.py
imports: from __future__ import division
  from unittest import TestCase
  from parameterized import parameterized
  from numpy import nan
  from pandas import DataFrame, date_range, Timedelta, concat
  from ..tears import create_returns_tear_sheet, create_information_tear_sheet, create_turnover_tear_sheet, create_summary_tear_sheet, create_full_tear_sheet, create_event_returns_tear_sheet, create_event_study_tear_sheet
  from ..utils import get_clean_factor_and_forward_returns
label_desc: Use image node_id 1 for calling the TearsTestCase obj's underlying member method code with example usage: obj.__localize_prices_and_factor(prices, factor, tz) and returns: prices,  factor