code: def test_resample_groupby_agg_object_dtype_all_nan(consolidate):
      # https://github.com/pandas-dev/pandas/issues/39329
  
      dates = date_range("2020-01-01", periods=15, freq="D")
      df1 = DataFrame(
          {
              "key": "A",
              "date": dates,
              "col1": range(15),
              "col_object": "val",
          }
      )
      df2 = DataFrame({"key": "B", "date": dates, "col1": range(15)})
      df = pd.concat([df1, df2], ignore_index=True)
      if consolidate:
          df = df._consolidate()
  
      with tm.assert_produces_warning(FutureWarning):
          result = df.groupby(["key"]).resample("W", on="date").min()
      idx = pd.MultiIndex.from_arrays(
          [
              ["A"] * 3 + ["B"] * 3,
              pd.to_datetime(
                  ["2020-01-05", "2020-01-12", "2020-01-19"] * 2
              ).as_unit("ns"),
          ],
          names=["key", "date"],
      )
      expected = DataFrame(
          {
              "key": ["A"] * 3 + ["B"] * 3,
              "col1": [0, 5, 12] * 2,
              "col_object": ["val"] * 3 + [np.nan] * 3,
          },
          index=idx,
      )
      tm.assert_frame_equal(result, expected)
  
imports: from textwrap import dedent
  import numpy
  import pytest
  from pandas.compat import is_platform_windows
  import pandas
  from pandas import DataFrame, Index, Series, TimedeltaIndex, Timestamp
  import pandas._testing
  from pandas.core.indexes.datetimes import date_range
label_desc: Use image node_id 23 for calling a global function with example usage: test_resample_groupby_agg_object_dtype_all_nan(consolidate) without return types