code: def test_hour(self):
      dr = date_range(
          start=Timestamp("2000-02-27"), periods=5, freq="h"
      )
      r1 = Index([x.to_julian_date() for x in dr])
      r2 = dr.to_julian_date()
      assert isinstance(r2, Index) and r2.dtype == np.float64
      tm.assert_index_equal(r1, r2)
  
file_path: pandas/pandas/tests/indexes/datetimes/methods/test_to_julian_date.py
imports: import numpy
  from pandas import Index, Timestamp, date_range
  import pandas._testing
label_desc: Use image node_id 3 for calling the TestDateTimeIndexToJulianDate obj's underlying member method code with example usage: obj.test_hour() without return types