code: def perimeter(self):
          '''
          Sum of the length of all sides, float.
          '''
          return sum([a.distance(b) for a, b in self.pairs()]f perimeter(self):
          '''
          Sum of the length of all sides, float.
          '''
          return sum([a.distance(b) for a, b in self.pairs()])
docs: Sum of the length of all sides, float.