class_docstr: Implement the PE function. 
code: def forward(self, feat, **kwargs):
      feat = feat + self.pe[:, : paddle.shape(feat)[1]]  # pe 1*5000*512
      return self.dropout(feat)
  
imports: import copy
  import math
  import paddle
  from paddle import nn
  from paddle.nn import functional
label_desc: Use image node_id 2 for calling the PositionalEncoding obj's underlying member method code with example usage: obj.forward(feat) and returns: self