code: def test_set_index_cast_datetimeindex(self):
      df = DataFrame(
          {
              "A": [
                  datetime(2000, 1, 1) + timedelta(i)
                  for i in range(1000)
              ],
              "B": np.random.default_rng(2).standard_normal(1000),
          }
      )
  
      idf = df.set_index("A")
      assert isinstance(idf.index, DatetimeIndex)
  
imports: from datetime import datetime, timedelta
  import numpy
  import pytest
  from pandas import Categorical, CategoricalIndex, DataFrame, DatetimeIndex, Index, MultiIndex, Series, date_range, period_range, to_datetime
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestSetIndex obj's underlying member method code with example usage: obj.test_set_index_cast_datetimeindex() without return types