code: def test_combine_first_timezone3(self, unit):
      dts1 = pd.DatetimeIndex(
          ["2011-01-01", "NaT", "2011-01-03", "2011-01-04"],
          tz="US/Eastern",
      ).as_unit(unit)
      df1 = DataFrame({"DATE": dts1}, index=[1, 3, 5, 7])
      dts2 = pd.DatetimeIndex(
          ["2012-01-01", "2012-01-02", "2012-01-03"], tz="US/Eastern"
      ).as_unit(unit)
      df2 = DataFrame({"DATE": dts2}, index=[2, 4, 5])
  
      res = df1.combine_first(df2)
      exp_dts = pd.DatetimeIndex(
          [
              "2011-01-01",
              "2012-01-01",
              "NaT",
              "2012-01-02",
              "2011-01-03",
              "2011-01-04",
          ],
          tz="US/Eastern",
      ).as_unit(unit)
      exp = DataFrame({"DATE": exp_dts}, index=[1, 2, 3, 4, 5, 7])
      tm.assert_frame_equal(res, exp)
  
imports: from datetime import datetime
  import numpy
  import pytest
  from pandas.core.dtypes.cast import find_common_type
  from pandas.core.dtypes.common import is_dtype_equal
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 11 for calling the TestDataFrameCombineFirst obj's underlying member method code with example usage: obj.test_combine_first_timezone3(unit) without return types