old_contents: import pandas as pd
  
  from vivarium.framework.population import PopulationView
  
  
  class DummyPopulationManager:
      def __init__(self):
          self._population = pd.DataFrame({'age': [0, 10, 20, 30, 40, 50, 60, 70], 'sex': ['Male', 'Female']*4})
  
  
  def test_create_PopulationView_with_all_columns():
      manager = DummyPopulationManager()
      view = PopulationView(manager)
      assert set(view.columns) == {'age', 'sex'}
  
new_contents: import pandas as pd
  
  from vivarium.framework.population import PopulationView
  
  
  class DummyPopulationManager:
      def __init__(self):
          self.population = pd.DataFrame({'age': [0, 10, 20, 30, 40, 50, 60, 70], 'sex': ['Male', 'Female']*4})
  
  
  def test_create_PopulationView_with_all_columns():
      manager = DummyPopulationManager()
      view = PopulationView(manager)
      assert set(view.columns) == {'age', 'sex'}
  
subject: Fix test