code: def test_multi_ddpg_input():
      nb_actions = 2
  
      actor_observation_input1 = Input(
          shape=(2, 3), name="actor_observation_input1"
      )
      actor_observation_input2 = Input(
          shape=(2, 4), name="actor_observation_input2"
      )
      actor = Sequential()
      x = Concatenate()(
          [actor_observation_input1, actor_observation_input2]
      )
      x = Flatten()(x)
      x = Dense(nb_actions)(x)
      actor = Model(
          inputs=[actor_observation_input1, actor_observation_input2],
          outputs=x,
      )
  
      action_input = Input(shape=(nb_actions,), name="action_input")
      critic_observation_input1 = Input(
          shape=(2, 3), name="critic_observation_input1"
      )
      critic_observation_input2 = Input(
          shape=(2, 4), name="critic_observation_input2"
      )
      x = Concatenate()(
          [critic_observation_input1, critic_observation_input2]
      )
      x = Concatenate()([action_input, Flatten()(x)])
      x = Dense(1)(x)
      critic = Model(
          inputs=[
              action_input,
              critic_observation_input1,
              critic_observation_input2,
          ],
          outputs=x,
      )
  
      processor = MultiInputProcessor(nb_inputs=2)
      memory = SequentialMemory(limit=10, window_length=2)
      agent = DDPGAgent(
          actor=actor,
          critic=critic,
          critic_action_input=action_input,
          memory=memory,
          nb_actions=2,
          nb_steps_warmup_critic=5,
          nb_steps_warmup_actor=5,
          batch_size=4,
          processor=processor,
      )
      agent.compile("sgd")
      agent.fit(MultiInputTestEnv([(3,), (4,)]), nb_steps=10)
  
file_path: keras-rl/tests/rl/agents/test_ddpg.py
imports: from __future__ import division
  from __future__ import absolute_import
  import pytest
  import numpy
  from numpy.testing import assert_allclose
  from keras.models import Model, Sequential
  from keras.layers import Input, Dense, Flatten, Concatenate
  from rl.agents.ddpg import DDPGAgent
  from rl.memory import SequentialMemory
  from rl.processors import MultiInputProcessor
  from ..util import MultiInputTestEnv
label_desc: Use image node_id 2 for calling a global function with example usage: test_multi_ddpg_input() without return types