code: def forward(self, x):
      l, bn = self._sub_layers.values()
      x = l(x)
      return paddle.reshape(bn(x.flatten(0, 1)), x.shape)
  
imports: import itertools
  import math
  import warnings
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle.nn.initializer import Constant
  from paddle.nn.initializer import TruncatedNormal
  from paddle.regularizer import L2Decay
  from .vision_transformer import Identity
  from .vision_transformer import ones_
  from .vision_transformer import trunc_normal_
  from .vision_transformer import zeros_
label_desc: Use image node_id 2 for calling the Linear_BN obj's underlying member method code with example usage: obj.forward(x) and returns: paddle