code: def forward_post(self, tgt, tgt_mask, query_pos):
      q = k = self.with_pos_embed(tgt, query_pos)
      tgt2 = self.self_attn(q, k, value=tgt, attn_mask=tgt_mask)
      tgt = tgt + self.dropout(tgt2)
      tgt = self.norm(tgt)
  
      return tgt
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.cvlibs import param_init
  from paddlepanseg.models.param_init import c2_xavier_fill, THLinearInitMixin, th_linear_fill, th_multihead_fill
  from .common import Conv2D, PositionEmbeddingSine
label_desc: Use image node_id 4 for calling the SelfAttentionLayer obj's underlying member method code with example usage: obj.forward_post(tgt, tgt_mask, query_pos) and returns: tgt