class_docstr: Test TransRAC utils
code: def test_similarity_matrix(self):
      q = torch.rand(1, 3)
      k = torch.rand(1, 3)
      v = torch.rand(1, 3)
      get_sim = SimilarityMatrix(input_dim=3)
      sim = get_sim(q, k, v)
      self.assertTrue(sim.shape == (1, 4, 1, 1))
  
imports: import unittest
  import torch
  from towhee.models.transrac import DenseMap, SimilarityMatrix
label_desc: Use image node_id 2 for calling the TestUtils obj's underlying member method code with example usage: obj.test_similarity_matrix() without return types