code: def test_is_copy(self, date_range_frame):
      # GH-27357, GH-30784: ensure the result of asof is an actual copy and
      # doesn't track the parent dataframe / doesn't give SettingWithCopy warnings
      df = date_range_frame.astype({"A": "float"})
      N = 50
      df.loc[df.index[15:30], "A"] = np.nan
      dates = date_range("1/1/1990", periods=N * 3, freq="25s")
  
      result = df.asof(dates)
  
      with tm.assert_produces_warning(None):
          result["C"] = 1
  
file_path: pandas/pandas/tests/frame/methods/test_asof.py
imports: import numpy
  import pytest
  from pandas._libs.tslibs import IncompatibleFrequency
  from pandas import DataFrame, Period, Series, Timestamp, date_range, period_range, to_datetime
  import pandas._testing
label_desc: Use image node_id 7 for calling the TestFrameAsof obj's underlying member method code with example usage: obj.test_is_copy(date_range_frame) without return types