fix: fix HyperparameterTuner.attach for Marketplace algorithms (#1291)

The AlgorithmSpecification for a training job that is part of
a hyperparameter tuning job will have TrainingImage set to "",
rather than not being present in the training job description.
Looking for AlgorithmName first, instead of TrainingImage,
fixes the issue of algorithm_arn not being populated when
attaching a hyperparameter tuning job.

Author: laurenyu

src/sagemaker/estimator.py

@@ -753,10 +753,10 @@ class constructor
         has_hps = "HyperParameters" in job_details
         init_params["hyperparameters"] = job_details["HyperParameters"] if has_hps else {}
 
-        if "TrainingImage" in job_details["AlgorithmSpecification"]:
-            init_params["image"] = job_details["AlgorithmSpecification"]["TrainingImage"]
-        elif "AlgorithmName" in job_details["AlgorithmSpecification"]:
+        if "AlgorithmName" in job_details["AlgorithmSpecification"]:
             init_params["algorithm_arn"] = job_details["AlgorithmSpecification"]["AlgorithmName"]
+        elif "TrainingImage" in job_details["AlgorithmSpecification"]:
+            init_params["image"] = job_details["AlgorithmSpecification"]["TrainingImage"]
         else:
             raise RuntimeError(
                 "Invalid AlgorithmSpecification. Either TrainingImage or "

tests/unit/test_estimator.py

@@ -2289,11 +2289,11 @@ def test_prepare_init_params_from_job_description_with_image_training_job():
 
 
 def test_prepare_init_params_from_job_description_with_algorithm_training_job():
-
     algorithm_job_description = RETURNED_JOB_DESCRIPTION.copy()
     algorithm_job_description["AlgorithmSpecification"] = {
         "TrainingInputMode": "File",
         "AlgorithmName": "arn:aws:sagemaker:us-east-2:1234:algorithm/scikit-decision-trees",
+        "TrainingImage": "",
     }
 
     init_params = EstimatorBase._prepare_init_params_from_job_description(