code: def test_flatten(self):
      def f():
          return reshape.Flatten(preserve_dims=2)(
              jnp.zeros([2, 3, 4, 5])
          )
  
      init_fn, apply_fn = transform.transform(f)
      params = init_fn(None)
      self.assertEqual(apply_fn(params, None).shape, (2, 3, 20))
  
imports: import unittest
  from absl.testing import absltest
  from absl.testing import parameterized
  from haiku._src import reshape
  from haiku._src import test_utils
  from haiku._src import transform
  import jax
  from jax.experimental import jax2tf
  import jax.numpy
  import numpy
label_desc: Use image node_id 5 for calling the ReshapeTest obj's underlying member method code with example usage: obj.test_flatten() and returns: reshape