text: __all__ = ['values_to_choices', 'choices_to_values']
  def values_to_choices(values):
      '''Given a list of strings, convert them to a choices tuple for the choices 
      attribute for any model Field.'''
      assert isinstance(values, (tuple, list))
      assert len(values) > 0
      for value in values:
          assert isinstance(value, basestring)
          assert len(value) > 0
      assert len(values) == len(set(values)) # Ensure no duplicates
  
      return tuple( [(value, value) for value in values] )
  
  
  def choices_to_values(choices):
      '''Gets all the values from the choices attribute for any model Field.'''
      assert isinstance(choices, tuple)
      for choice in choices:
          assert isinstance(choice, tuple)
          assert len(choice) == 2
  
      return [choice[0] for choice in choices]
  