code: def test_forward(self):
      batch = 16
      len1, len2 = 21, 24
      seq_len1 = torch.randint(
          low=len1 - 10, high=len1 + 1, size=(batch,)
      ).long()
      seq_len2 = torch.randint(
          low=len2 - 10, high=len2 + 1, size=(batch,)
      ).long()
  
      mask1 = []
      for w in seq_len1:
          mask1.append([1] * w.item() + [0] * (len1 - w.item()))
      mask1 = torch.tensor(mask1, dtype=torch.bool)
      mask2 = []
      for w in seq_len2:
          mask2.append([1] * w.item() + [0] * (len2 - w.item()))
      mask2 = torch.tensor(mask2, dtype=torch.bool)
  
      d = 200  # hidden dimension
      n = 20  # number of perspective
      test1 = torch.randn(batch, len1, d)
      test2 = torch.randn(batch, len2, d)
      test1 = test1 * mask1.view(-1, len1, 1).expand(-1, len1, d)
      test2 = test2 * mask2.view(-1, len2, 1).expand(-1, len2, d)
  
      test1_fw, test1_bw = torch.split(test1, d // 2, dim=-1)
      test2_fw, test2_bw = torch.split(test2, d // 2, dim=-1)
  
      ml_fw = BiMpmMatching.from_params(
          Params({"is_forward": True, "num_perspectives": n})
      )
      ml_bw = BiMpmMatching.from_params(
          Params({"is_forward": False, "num_perspectives": n})
      )
  
      vecs_p_fw, vecs_h_fw = ml_fw(test1_fw, mask1, test2_fw, mask2)
      vecs_p_bw, vecs_h_bw = ml_bw(test1_bw, mask1, test2_bw, mask2)
      vecs_p, vecs_h = (
          torch.cat(vecs_p_fw + vecs_p_bw, dim=2),
          torch.cat(vecs_h_fw + vecs_h_bw, dim=2),
      )
  
      assert vecs_p.size() == torch.Size([batch, len1, 10 + 10 * n])
      assert vecs_h.size() == torch.Size([batch, len2, 10 + 10 * n])
      assert (
          ml_fw.get_output_dim()
          == ml_bw.get_output_dim()
          == vecs_p.size(2) // 2
          == vecs_h.size(2) // 2
      )
  
imports: import torch
  from allennlp.common import Params
  from allennlp.modules import BiMpmMatching
  from allennlp.common.testing import AllenNlpTestCase
label_desc: Use image node_id 1 for calling the TestBiMPMMatching obj's underlying member method code with example usage: obj.test_forward() without return types