code: def natsorted(seq, key=lambda x: x, number_type=float, signed=True, exp=True):
      
      return sorted(seq, key=lambda x: natsort_key(key(x),
                                                   number_type=number_type,
                                                   signed=signed, exp=exp))
docs: \
      Sorts a sequence naturally (alphabetically and numerically),
      not lexicographically.
  
          >>> a = ['num3', 'num5', 'num2']
          >>> natsorted(a)
          ['num2', 'num3', 'num5']
          >>> b = [('a', 'num3'), ('b', 'num5'), ('c', 'num2')]
          >>> from operator import itemgetter
          >>> natsorted(b, key=itemgetter(1))
          [('c', 'num2'), ('a', 'num3'), ('b', 'num5')]