Allow passing google auth Credentials directly to GCS connector

parsons/google/google_cloud_storage.py

@@ -1,14 +1,15 @@
 import datetime
 import gzip
-import petl
 import logging
 import time
 import uuid
 import zipfile
-from typing import Optional
+from typing import Optional, Union
 
 import google
+import petl
 from google.cloud import storage, storage_transfer
+from google.oauth2.credentials import Credentials
 
 from parsons.google.utilities import (
     load_google_application_credentials,
@@ -45,10 +46,16 @@ class GoogleCloudStorage(object):
         GoogleCloudStorage Class
     """
 
-    def __init__(self, app_creds=None, project=None):
-        env_credentials_path = str(uuid.uuid4())
-        setup_google_application_credentials(app_creds, target_env_var_name=env_credentials_path)
-        credentials = load_google_application_credentials(env_credentials_path)
+    def __init__(self, app_creds: Optional[Union[str, dict, Credentials]] = None, project=None):
+        if isinstance(app_creds, Credentials):
+            credentials = app_creds
+        else:
+            env_credentials_path = str(uuid.uuid4())
+            setup_google_application_credentials(
+                app_creds, target_env_var_name=env_credentials_path
+            )
+            credentials = load_google_application_credentials(env_credentials_path)
+
         self.project = project
 
         # Throws an error if you pass project=None, so adding if/else statement.