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