docs: def mean(data):
      """Return the sample arithmetic mean of data.
  
      >>> mean([1, 2, 3, 4, 4])
      2.8
  
      >>> from fractions import Fraction as F
      >>> mean([F(3, 7), F(1, 21), F(5, 3), F(1, 3)])
      Fraction(13, 21)
  
      >>> from decimal import Decimal as D
      >>> mean([D("0.5"), D("0.75"), D("0.625"), D("0.375")])
      Decimal('0.5625')
  
      If ``data`` is empty, StatisticsError will be raised.
      """
      if iter(data) is data:
          data = list(data)
      n = len(data)
      if n < 1:
          raise StatisticsError('mean requires at least one data point')
      return _sum(data)/n