code: def forward(self, input):
      return input.view(input.size(0), -1)
  
imports: from abc import ABC
  import numpy
  from ray.rllib.models.modelv2 import restore_original_dimensions
  from ray.rllib.models.preprocessors import get_preprocessor
  from ray.rllib.models.torch.torch_modelv2 import TorchModelV2
  from ray.rllib.utils.framework import try_import_torch
label_desc: Use image node_id 1 for calling the Flatten obj's underlying member method code with example usage: obj.forward(input) and returns: input