code: def variance(numbers, type='population'):
      
      mean = average(numbers)
      variance = 0
      for number in numbers:
          variance += (mean - number) ** 2
  
      if type == 'population':
          return variance / len(numbers)
      else:
          return variance / (len(numbers) - 1)
docs: Calculates the population or sample variance of a list of numbers.
      A large number means the results are all over the place, while a
      small number means the results are comparatively close to the average.
  
      Args:
          numbers: a list  of integers or floating point numbers to compare.
  
          type: string, 'population' or 'sample', the kind of variance to be computed.
  
      Returns:
          The computed population or sample variance.
          Defaults to population variance.
  
      Requires:
          The math module, average()