code: def test_simple_call(self):
      layer = tl.PositionalEncoding(max_len=8)
      x = np.array([[[2.0, 3.0, 4.0, 5.0], [1.0, 2.0, 3.0, 4.0]]])
      layer.init(shapes.signature(x))
      y = layer(x)
      self.assertEqual(y.shape, (1, 2, 4))
  
imports: import functools
  from absl.testing import absltest
  import numpy
  from trax import shapes
  import trax.layers
  from trax.layers import test_utils
label_desc: Use image node_id 1 for calling the PositionalEncodingTest obj's underlying member method code with example usage: obj.test_simple_call() without return types