code: def update(self, x_list=list(), y_list=list()):
          
          if not y_list:
              for x in x_list:
                  if x in self.x_list:
                      i = self.x_list.index(float(x))
                      self.x_list.pop(i)
                      self.y_list.pop(i)
          else:
              x_list = map(float, x_list)
              y_list = map(float, y_list)
              data = [(x, y) for x, y in zip(self.x_list, self.y_list) if x not in x_list]
              data.extend(zip(x_list, y_list))
              data = sorted(data)
              self.x_list = [float(x) for (x, y) in data]
              self.y_list = [float(y) for (x, y) in data]
docs: update interpolation data
          :param list(float) x_list: x values
          :param list(float) y_list: y values