code: def test_nunique_with_empty_series():
      # GH 12553
      data = Series(name="name", dtype=object)
      result = data.groupby(level=0).nunique()
      expected = Series(name="name", dtype="int64")
      tm.assert_series_equal(result, expected)
  
imports: import builtins
  import datetime
  from string import ascii_lowercase
  import numpy
  import pytest
  from pandas._libs.tslibs import iNaT
  import pandas
  from pandas import DataFrame, MultiIndex, Series, Timestamp, date_range, isna
  import pandas._testing
  from pandas.util import _test_decorators
label_desc: Use image node_id 35 for calling a global function with example usage: test_nunique_with_empty_series() without return types