code: def optimizer(request, backend):
      """
      Optimizer for given backend. Optimizer is expected to be passed via `request` as a string, i.e. "Adam".
  
      For tensorflow, the optimizer is an instantiated `tf.of.keras.optimizers.Optimizer` object. For pytorch,
      the optimizer is a `torch.optim.Optimizer` class (NOT instantiated).
      """
      optimizer = request.param  # Get parametrized setting
      if backend not in ("tensorflow", "pytorch", "keops"):
          pytest.skip(
              "`optimizer` only implemented for tensorflow, pytorch and keops."
          )
      if isinstance(optimizer, str):
          module = (
              "tensorflow.keras.optimizers"
              if backend == "tensorflow"
              else "torch.optim"
          )
          try:
              optimizer = getattr(import_module(module), optimizer)
          except AttributeError:
              raise ValueError(
                  f"{optimizer} is not a recognised optimizer in {module}."
              )
      return optimizer
  
imports: from functools import partial
  from importlib import import_module
  import numpy
  import tensorflow
  import torch
  import torch.nn
  from sklearn.ensemble import RandomForestClassifier
  from xgboost import XGBClassifier
  from requests.exceptions import HTTPError
  import pytest
  from pytest_cases import fixture, parametrize
  from transformers import AutoTokenizer
  from alibi_detect.cd.pytorch import UAE
  from alibi_detect.cd.pytorch import preprocess_drift
  from alibi_detect.cd.tensorflow import UAE
  from alibi_detect.cd.tensorflow import preprocess_drift
  from alibi_detect.utils.pytorch.kernels import GaussianRBF
  from alibi_detect.utils.pytorch.kernels import DeepKernel
  from alibi_detect.utils.tensorflow.kernels import GaussianRBF
  from alibi_detect.utils.tensorflow.kernels import DeepKernel
  from alibi_detect.models.pytorch import TransformerEmbedding
  from alibi_detect.models.tensorflow import TransformerEmbedding
  from alibi_detect.cd.pytorch import HiddenOutput
  from alibi_detect.cd.tensorflow import HiddenOutput
  from alibi_detect.utils.frameworks import has_keops
label_desc: Use image node_id 5 for calling a global function with example usage: optimizer(request, backend) and returns: optimizer