code: def setUp(self):
      self.coder = MultiboxCoder(
          self.grids,
          self.aspect_ratios,
          self.steps,
          self.sizes,
          (0.1, 0.2),
      )
      self.n_bbox = sum(
          grid * grid * (len(ar) + 1) * 2
          for grid, ar in zip(self.grids, self.aspect_ratios)
      )
      self.bbox = _random_array((5, 4))
      self.label = np.random.randint(0, self.n_fg_class, size=5)
      self.mb_loc = _random_array((self.n_bbox, 4))
      self.mb_conf = _random_array((self.n_bbox, self.n_fg_class + 1))
  
file_path: chainercv/tests/links_tests/model_tests/ssd_tests/test_multibox_coder.py
imports: import numpy
  import unittest
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links.model.ssd import MultiboxCoder
label_desc: Use image node_id 1 for calling the TestMultiboxCoder obj's underlying member method code with example usage: obj.setUp() without return types