code: def _call(self, x):
          
          result = 0
          for i in range(0, self.domain.size - 1):
              result += (self.scale * (x[i + 1] - x[i] ** 2) ** 2 +
                         (x[i] - 1) ** 2)
  
          return result
docs: Return ``self(x)``.