class_docstr: Implements FFN equation.
code: def forward(self, x):
      return self.w_2(self.dropout(F.relu(self.w_1(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 PositionwiseFeedForward obj's underlying member method code with example usage: obj.forward(x) and returns: self