old_contents: 
  from unittest import TestCase
  
  from traitlets import TraitError
  
  from ipywidgets import FloatSlider
  
  
  class TestFloatSlider(TestCase):
  
      def test_construction(self):
          FloatSlider()
  
      def test_construction_readout_format(self):
          slider = FloatSlider(readout_format='$.1f')
          assert slider.get_state()['readout_format'] == '$.1f'
  
      def test_construction_invalid_readout_format(self):
          with self.assertRaises(TraitError):
              FloatSlider(readout_format='broken')
  
new_contents: # Copyright (c) Jupyter Development Team.
  # Distributed under the terms of the Modified BSD License.
  
  from unittest import TestCase
  
  from traitlets import TraitError
  
  from ipywidgets import FloatSlider
  
  
  class TestFloatSlider(TestCase):
  
      def test_construction(self):
          FloatSlider()
  
      def test_construction_readout_format(self):
          slider = FloatSlider(readout_format='$.1f')
          assert slider.get_state()['readout_format'] == '$.1f'
  
      def test_construction_invalid_readout_format(self):
          with self.assertRaises(TraitError):
              FloatSlider(readout_format='broken')
  
subject: Add copyright notice