code: def test_loc_datetime_no_freq():
      # https://github.com/dask/dask/issues/2389
  
      datetime_index = pd.date_range(
          "2016-01-01", "2016-01-31", freq="12h"
      )
      datetime_index.freq = None  # FORGET FREQUENCY
      df = pd.DataFrame(
          {"num": range(len(datetime_index))}, index=datetime_index
      )
  
      ddf = dd.from_pandas(df, npartitions=1)
      slice_ = slice("2016-01-03", "2016-01-05")
      result = ddf.loc[slice_, :]
      expected = df.loc[slice_, :]
      assert_eq(result, expected)
  
imports: from __future__ import annotations
  import contextlib
  import numpy
  import pandas
  import pytest
  import dask
  import dask.dataframe
  from dask.base import tokenize
  from dask.dataframe._compat import PANDAS_GE_210, PANDAS_GE_220, IndexingError, tm
  from dask.dataframe.indexing import _coerce_loc_index
  from dask.dataframe.utils import assert_eq, make_meta, pyarrow_strings_enabled
label_desc: Use image node_id 19 for calling a global function with example usage: test_loc_datetime_no_freq() without return types