new_contents: from conference_scheduler.resources import Event
  
  
  def test_can_construct_event():
      e = Event(
          name='example',
          duration=60,
          demand=100,
          tags=['beginner', 'python'],
          unavailability=[]
      )
      assert isinstance(e, Event)
      assert e.name == 'example'
      assert e.tags == ['beginner', 'python']
      assert e.unavailability == []
  
  
  def test_optional_args_to_event_are_defaulted():
      e = Event(name='example', duration=60, demand=100)
      assert e.tags == []
      assert e.unavailability == []
  
  
  def test_optional_args_are_safely_mutable():
      # Construct an instance of `Event` with the optional arguments,
      # omitted, then assign it a tag
      e = Event(name='example', duration=60, demand=100)
      assert e.tags == []
      e.tags.append('intermediate')
      assert e.tags == ['intermediate']
  
      # Now create a second instance of `Event`, and check we haven't
      # polluted the default arguments.
      f = Event(name='another example', duration=30, demand=50)
      assert f.tags == []
  
subject: Add tests for optional arguments on Event