code: import numpy as np
  import pytest
  
  from pandas import Series
  from pandas.core.construction import create_series_with_explicit_dtype
  
  
  @pytest.mark.parametrize(
      "data, expected",
      [
          (np.random.randint(0, 10, size=1000), False),
          (np.arange(1000), True),
          ([], True),
          ([np.nan], True),
          (["foo", "bar", np.nan], True),
          (["foo", "foo", np.nan], False),
          (["foo", "bar", np.nan, np.nan], False),
      ],
  )
  def test_is_unique(data, expected):
      # GH#11946 / GH#25180
      ser = create_series_with_explicit_dtype(data, dtype_if_empty=object)
      assert ser.is_unique is expected
  
  
  def test_is_unique_class_ne(capsys):
      # GH#20661
      class Foo:
          def __init__(self, val):
              self._value = val
  
          def __ne__(self, other):
              raise Exception("NEQ not supported")
  
      with capsys.disabled():
          li = [Foo(i) for i in range(5)]
          ser = Series(li, index=list(range(5)))
  
      ser.is_unique
      captured = capsys.readouterr()
      assert len(captured.err) == 0
  