feat(examples): Add S3 auth by passing env variables

This commit allows S3 authentication by passing in environmental
variables `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and
`AWS_ENDPOINT_URL_`. If `AWS_ENDPOINT_URL_` is not found in `env`,
it is given `default_s3_read_endpoint` for `rb` mode and
`default_s3_write_endpint` for `wb` mode.

examples/hf_serialization.py

@@ -28,6 +28,16 @@
 
 from tensorizer import TensorDeserializer, TensorSerializer, stream_io, utils
 
+s3_access_key_id = os.environ.get("AWS_ACCESS_KEY_ID")
+s3_secret_access_key = os.environ.get("AWS_SECRET_ACCESS_KEY")
+
+if os.environ.get("AWS_ENDPOINT_URL"):
+    default_s3_read_endpoint = os.environ.get("AWS_ENDPOINT_URL")
+    default_s3_write_endpoint = os.environ.get("AWS_ENDPOINT_URL")
+else:
+    default_s3_read_endpoint = "accel-object.ord1.coreweave.com"
+    default_s3_write_endpoint = "object.ord1.coreweave.com"
+
 # Setup logger
 logger = logging.getLogger(__name__)
 logger.setLevel(level=logging.INFO)
@@ -54,7 +64,13 @@ def check_file_exists(
     if os.path.exists(file):
         return True
     else:
-        with stream_io.open_stream(file, "rb") as f:
+        with stream_io.open_stream(
+            file,
+            "wb",
+            s3_access_key_id,
+            s3_secret_access_key,
+            default_s3_read_endpoint,
+        ) as f:
             if f.read(1) == b"":
                 return False
             else:
@@ -101,18 +117,31 @@ def serialize_model(
         config_path = f"{dir_prefix}-config.json"
         if (not config_file_exists) or force:
             logger.info(f"Writing config to {config_path}")
-            with stream_io.open_stream(config_path, "wb") as f:
+            with stream_io.open_stream(
+                config_path,
+                "wb",
+                s3_access_key_id,
+                s3_secret_access_key,
+                default_s3_write_endpoint,
+            ) as f:
                 if hasattr(config, "to_dict"):
                     f.write(bytes(json.dumps(config.to_dict()), "utf-8"))
                 elif isinstance(config, dict):
                     f.write(bytes(json.dumps(config), "utf-8"))
-                f.close()  ## Remove after PR
+                f.close()  ## Remove after PR merged
 
     if (not weights_file_exists) or force:
         logger.info(f"Writing tensors to {dir_prefix}.tensors")
-        ts = TensorSerializer(f"{dir_prefix}.tensors")
-        ts.write_module(model)
-        ts.close()
+        with stream_io.open_stream(
+            f"{dir_prefix}.tensors",
+            "wb",
+            s3_access_key_id,
+            s3_secret_access_key,
+            default_s3_write_endpoint,
+        ) as f:
+            ts = TensorSerializer(f)
+            ts.write_module(model)
+            ts.close()
 
 
 def load_model(