code: def forward(self, x):
      if x[0].dim() == 3 and x[1].dim() == 2:
          x[1] = x[1].unsqueeze(1).reshape_as(x[0])
      if x[1].dim() == 3 and x[0].dim() == 2:
          x[0] = x[0].unsqueeze(1).reshape_as(x[1])
      z = torch.cat(x, dim=x[0].dim() - 1)
      z = self.mlp(z)
      return z
  
imports: import torch
  import torch.nn
  import torch.nn.functional
  from mmf.common.registry import registry
  from mmf.utils.general import get_chunks, get_sizes_list, irfft, rfft
  from mmf.utils.logger import log_class_usage
label_desc: Use image node_id 2 for calling the ConcatMLP obj's underlying member method code with example usage: obj.forward(x) and returns: z