code: def __matmul__(self, x):
      return self.A @ x
  
imports: from functools import partial
  import unittest
  from absl.testing import absltest
  import numpy
  import scipy.sparse.linalg
  import jax
  import jax.numpy
  import jax.scipy.sparse.linalg
  from jax import jit
  from jax import lax
  from jax.tree_util import register_pytree_node_class
  import jax._src.scipy.sparse.linalg
  from jax._src import config
  from jax._src import dtypes
  from jax._src import test_util
label_desc: Use image node_id 2 for calling the CustomOperator obj's underlying member method code with example usage: obj.__matmul__(x) and returns: unknown