code: def test_simple_call(self):
      layer = sparsity.MultiplicativeModularCausalAttention(
          d_feature=4, n_heads=2, sparsity=2
      )
      x = np.array(
          [
              [
                  [2, 5, 3, 4],
                  [0, 1, 2, 3],
                  [0, 1, 2, 3],
              ]
          ]
      )
      _, _ = layer.init(shapes.signature(x))
  
      y = layer(x)
      self.assertEqual(y.shape, (1, 3, 4))
  
imports: import functools
  from absl.testing import parameterized
  import jax
  import numpy
  from tensorflow import test
  from trax import fastmath
  from trax import shapes
  import trax.layers
  from trax.layers import test_utils
  from trax.layers.research import sparsity
label_desc: Use image node_id 1 for calling the MultiplicativeModularCausalAttentionTest obj's underlying member method code with example usage: obj.test_simple_call() without return types