code: def test_dti_is_month_start(self):
      dti = DatetimeIndex(["2000-01-01", "2000-01-02", "2000-01-03"])
  
      assert dti.is_month_start[0] == 1
  
imports: import calendar
  from datetime import date, datetime, time
  import locale
  import unicodedata
  import numpy
  import pytest
  from pandas._libs.tslibs import timezones
  from pandas import DatetimeIndex, Index, NaT, Timestamp, date_range, offsets
  import pandas._testing
  from pandas.core.arrays import DatetimeArray
label_desc: Use image node_id 14 for calling the TestDatetimeIndexOps obj's underlying member method code with example usage: obj.test_dti_is_month_start() without return types