code: def forward(self, inputs, mask):
      pass
  
imports: import torch
  import numpy
  import pytest
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.modules.seq2seq_encoders import ComposeEncoder, FeedForwardEncoder, Seq2SeqEncoder
  from allennlp.modules import FeedForward
label_desc: Use image node_id 2 for calling the MockSeq2SeqEncoder obj's underlying member method code with example usage: obj.forward(inputs, mask) without return types