Support Leaderboard API(#94)

Added predictor.leaderboard() API support

src/autogluon/cloud/predictor/cloud_predictor.py

@@ -1,7 +1,9 @@
 from __future__ import annotations
 
+import io
 import logging
 import os
+import tarfile
 from abc import ABC, abstractmethod
 from datetime import datetime
 from typing import Any, Dict, Optional, Tuple, Union
@@ -132,6 +134,24 @@ def info(self) -> Dict[str, Any]:
         )
         return info
 
+    def leaderboard(self) -> pd.DataFrame:
+        info = self.backend.get_fit_job_info()
+        cloud_output_path = self.cloud_output_path
+        path = os.path.join(cloud_output_path, "model", info["name"], "output/output.tar.gz")
+        assert is_s3_url(path), "Please provide a valid s3 path to the leaderboard result."
+        bucket, key = s3_path_to_bucket_prefix(path)
+        s3 = boto3.client("s3")
+        try:
+            wholefile = s3.get_object(Bucket=bucket, Key=key)["Body"].read()
+            fileobj = io.BytesIO(wholefile)
+            tarf = tarfile.open(fileobj=fileobj)
+            leaderboard = tarf.extractfile("leaderboard.csv")
+            df = pd.read_csv(leaderboard)
+            return df
+        except Exception:
+            empty = pd.DataFrame()
+            return empty
+
     def _setup_local_output_path(self, path):
         if path is None:
             utcnow = datetime.utcnow()