code: def test_retrieve_hosting_prepacked_artifact_key(self):
      test_spec = copy.deepcopy(BASE_SPEC)
  
      test_spec["hosting_prepacked_artifact_key"] = "some/thing"
  
      test_spec["hosting_instance_type_variants"] = {
          "regional_aliases": {
              "us-west-2": {
                  "alias_ecr_uri_1": "763104351884.dkr.ecr.us-west-2.ama"
                  "zonaws.com/djl-inference:0.23.0-deepspeed0.9.5-cu118"
              }
          },
          "variants": {
              "c4": {
                  "regional_properties": {
                      "image_uri": "$alias_ecr_uri_1",
                  },
                  "properties": {
                      "prepacked_artifact_key": "in/the/way",
                  },
              }
          },
      }
  
      self.assertEqual(
          _retrieve_hosting_prepacked_artifact_key(
              JumpStartModelSpecs(test_spec),
              instance_type="ml.c4.xlarge",
          ),
          "in/the/way",
      )
  
      test_spec["hosting_prepacked_artifact_key"] = None
  
      self.assertEqual(
          _retrieve_hosting_prepacked_artifact_key(
              JumpStartModelSpecs(test_spec),
              instance_type="ml.c4.xlarge",
          ),
          "in/the/way",
      )
  
      test_spec["hosting_instance_type_variants"] = None
  
      self.assertEqual(
          _retrieve_hosting_prepacked_artifact_key(
              JumpStartModelSpecs(test_spec),
              instance_type="ml.c4.xlarge",
          ),
          None,
      )
  
      test_spec["hosting_prepacked_artifact_key"] = "shemoves"
  
      self.assertEqual(
          _retrieve_hosting_prepacked_artifact_key(
              JumpStartModelSpecs(test_spec),
              instance_type="ml.c4.xlarge",
          ),
          "shemoves",
      )
  
imports: from __future__ import absolute_import
  import unittest
  from unittest.mock import Mock
  from mock.mock import patch
  import pytest
  import copy
  from sagemaker.jumpstart import artifacts
  from sagemaker.jumpstart.artifacts.model_uris import _retrieve_hosting_prepacked_artifact_key, _retrieve_hosting_artifact_key, _retrieve_training_artifact_key
  from sagemaker.jumpstart.types import JumpStartModelSpecs
  from tests.unit.sagemaker.jumpstart.constants import BASE_SPEC
  from sagemaker.jumpstart.artifacts.model_packages import _retrieve_model_package_arn
  from sagemaker.jumpstart.artifacts.model_uris import _retrieve_model_uri
  from sagemaker.jumpstart.enums import JumpStartScriptScope
  from tests.unit.sagemaker.jumpstart.utils import get_spec_from_base_spec, get_special_model_spec
  from tests.unit.sagemaker.workflow.conftest import mock_client
label_desc: Use image node_id 1 for calling the ModelArtifactVariantsTest obj's underlying member method code with example usage: obj.test_retrieve_hosting_prepacked_artifact_key() without return types