code: def forward(self, x, xyz):
      # add position embedding
      xyz = xyz.permute(0, 2, 1)
      xyz = self.conv_pos(xyz)
  
      x = self.relu(self.bn1(self.conv1(x)))  # B, D, N
  
      x1 = self.sa1(x, xyz)
      x2 = self.sa2(x1, xyz)
      x3 = self.sa3(x2, xyz)
      x4 = self.sa4(x3, xyz)
  
      x = torch.cat((x1, x2, x3, x4), dim=1)
  
      return x
  
imports: import torch
  from helper import TransitionDown
  from torch import nn
label_desc: Use image node_id 2 for calling the PCTPositionEmbedding obj's underlying member method code with example usage: obj.forward(x, xyz) and returns: x