docs: def preprocess_x_y(x, y):
      """Preprocess x, y input data. Returns list of list style.
  
      **中文文档**
  
      预处理输入的x, y数据。
      """
      def is_iterable_slicable(a):
          if hasattr(a, "__iter__") and hasattr(a, "__getitem__"):
              return True
          else:
              return False
  
      if is_iterable_slicable(x):
          if is_iterable_slicable(x[0]):
              return x, y
          else:
              return (x,), (y,)
      else:
          raise ValueError("invalid input!")