code: def _check_layer(self, layer, x, y, bits):
      self.assertEqual(layer.size.x, x)
      self.assertEqual(layer.size.y, y)
      self.assertEqual(layer.bits_per_pixel, bits)
  
imports: from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from pysc2.lib import actions
  from pysc2.lib import features
  from pysc2.lib import point
  from pysc2.lib import units
  from pysc2.tests import dummy_observation
  from s2clientprotocol import common_pb2
label_desc: Use image node_id 21 for calling the DummyObservationTest obj's underlying member method code with example usage: obj._check_layer(layer, x, y, bits) without return types