code: def forward(
      self, z_src: Tensor, z_dst: Tensor, raw_msg: Tensor, t_enc: Tensor
  ):
      return torch.cat([z_src, z_dst, raw_msg, t_enc], dim=-1)
  
imports: import copy
  from typing import Callable, Dict, Tuple
  import torch
  from torch import Tensor
  from torch.nn import GRUCell, Linear
  from torch_geometric.nn.inits import zeros
  from torch_geometric.utils import scatter
  from torch_geometric.utils._scatter import scatter_argmax
label_desc: Use image node_id 2 for calling the IdentityMessage obj's underlying member method code with example usage: obj.forward(z_src, z_dst, raw_msg, t_enc) and returns: torch