code: def test_delta_with_observations(es):
      four_delta = Timedelta(4, "observations")
      assert not four_delta.is_absolute()
      assert four_delta.get_value("o") == 4
  
      neg_four_delta = -four_delta
      assert not neg_four_delta.is_absolute()
      assert neg_four_delta.get_value("o") == -4
  
      time = pd.to_datetime("2019-05-01")
  
      error_txt = "Invalid unit"
      with pytest.raises(Exception, match=error_txt):
          time + four_delta
  
      with pytest.raises(Exception, match=error_txt):
          time - four_delta
  
imports: import pandas
  import pytest
  from dateutil.relativedelta import relativedelta
  from featuretools.entityset import Timedelta
  from featuretools.feature_base import Feature
  from featuretools.primitives import Count
  from featuretools.tests.testing_utils import to_pandas
  from featuretools.utils.wrangle import _check_timedelta
label_desc: Use image node_id 3 for calling a global function with example usage: test_delta_with_observations(es) without return types