code: def test_flax_layers():
      """
      One-off simple tests for Flax layers.
      Unfortunately, Flax layers have a different interface from other layers.
      """
      if not is_backend_tested("jax"):
          pytest.skip()
      else:
          import jax
          import jax.numpy as jnp
  
          import flax
          from flax import linen as nn
          from einops.layers.flax import EinMix, Reduce, Rearrange
  
          class NN(nn.Module):
              @nn.compact
              def __call__(self, x):
                  x = EinMix(
                      "b (h h2) (w w2) c -> b h w c_out",
                      "h2 w2 c c_out",
                      "c_out",
                      sizes=dict(h2=2, w2=3, c=4, c_out=5),
                  )(x)
                  x = Rearrange(
                      "b h w c -> b (w h c)", sizes=dict(c=5)
                  )(x)
                  x = Reduce("b hwc -> b", "mean", dict(hwc=2 * 3 * 5))(
                      x
                  )
                  return x
  
          model = NN()
          fixed_input = jnp.ones([10, 2 * 2, 3 * 3, 4])
          params = model.init(jax.random.PRNGKey(0), fixed_input)
          eval_at_point = lambda params: jnp.linalg.norm(
              model.apply(params, fixed_input)
          )
  
          vandg = jax.value_and_grad(eval_at_point)
          value0 = eval_at_point(params)
          value1, grad1 = vandg(params)
          assert jnp.allclose(value0, value1)
  
          params2 = jax.tree_map(
              lambda x1, x2: x1 - x2 * 0.001, params, grad1
          )
  
          value2 = eval_at_point(params2)
          assert value0 >= value2, (value0, value2)
  
          # check serialization
          fbytes = flax.serialization.to_bytes(params)
          _loaded = flax.serialization.from_bytes(params, fbytes)
  
file_path: einops/tests/test_layers.py
imports: import pickle
  import tempfile
  from collections import namedtuple
  import numpy
  import pytest
  from einops import rearrange, reduce
  from .None import collect_test_backends, is_backend_tested, FLOAT_REDUCTIONS
label_desc: Use image node_id 10 for calling a global function with example usage: test_flax_layers() and returns: x