code: def window_partition(x, window_size):
      """
      Args:
          x: (B, H, W, C)
          window_size (int): window size
      Returns:
          windows: (num_windows*B, window_size, window_size, C)
      """
      B, H, W, C = x.shape
      x = x.reshape(
          (
              B,
              H // window_size,
              window_size,
              W // window_size,
              window_size,
              C,
          )
      )
      windows = x.transpose((0, 1, 3, 2, 4, 5)).reshape(
          (-1, window_size, window_size, C)
      )
      return windows
  
imports: import math
  import paddle
  import paddle.nn
  import paddle.nn.functional
label_desc: Use image node_id 2 for calling a global function with example usage: window_partition(x, window_size) and returns: windows