code: def test_flatten_inputs_to_1d_tensor(self):
      # B=3; no time axis.
      check(
          flatten_np(self.struct, spaces_struct=self.spaces),
          np.array(
              [
                  [
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                      3.0,
                      8.0,
                      7.0,
                      6.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                  ],
                  [
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      4.0,
                      5.0,
                      6.0,
                      5.0,
                      4.0,
                      3.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                  ],
                  [
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      7.0,
                      8.0,
                      9.0,
                      2.0,
                      1.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      3.0,
                  ],
              ]
          ),
      )
  
      struct_tf = tree.map_structure(
          lambda s: tf.convert_to_tensor(s), self.struct
      )
      check(
          flatten_tf(struct_tf, spaces_struct=self.spaces),
          np.array(
              [
                  [
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                      3.0,
                      8.0,
                      7.0,
                      6.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                  ],
                  [
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      4.0,
                      5.0,
                      6.0,
                      5.0,
                      4.0,
                      3.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                  ],
                  [
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      7.0,
                      8.0,
                      9.0,
                      2.0,
                      1.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      3.0,
                  ],
              ]
          ),
      )
  
      struct_torch = tree.map_structure(
          lambda s: torch.from_numpy(s), self.struct
      )
      check(
          flatten_torch(struct_torch, spaces_struct=self.spaces),
          np.array(
              [
                  [
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                      3.0,
                      8.0,
                      7.0,
                      6.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                  ],
                  [
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      4.0,
                      5.0,
                      6.0,
                      5.0,
                      4.0,
                      3.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      2.0,
                  ],
                  [
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      7.0,
                      8.0,
                      9.0,
                      2.0,
                      1.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      1.0,
                      0.0,
                      0.0,
                      0.0,
                      0.0,
                      3.0,
                  ],
              ]
          ),
      )
  
imports: import gymnasium
  import numpy
  import tree
  import unittest
  import ray
  from ray.rllib.utils.framework import try_import_tf, try_import_torch
  from ray.rllib.utils.numpy import flatten_inputs_to_1d_tensor
  from ray.rllib.utils.numpy import make_action_immutable
  from ray.rllib.utils.test_utils import check
  from ray.rllib.utils.tf_utils import flatten_inputs_to_1d_tensor, l2_loss, one_hot
  from ray.rllib.utils.torch_utils import flatten_inputs_to_1d_tensor, l2_loss, one_hot
label_desc: Use image node_id 4 for calling the TestUtils obj's underlying member method code with example usage: obj.test_flatten_inputs_to_1d_tensor() without return types