[SDK] Use Training Client without Kube Config (#1740)

* [SDK] Use Training Client without Kube Config

* Skip kube-config when using client config

sdk/python/kubeflow/training/api/training_client.py

@@ -36,35 +36,32 @@
 class TrainingClient(object):
     def __init__(
         self,
-        config_file=None,
-        context=None,
-        client_configuration=None,
-        persist_config=True,
+        config_file: str = None,
+        context: str = None,
+        client_configuration: client.Configuration = None,
     ):
         """TrainingClient constructor.
 
         Args:
-            config_file: Name of the kube-config file. Defaults to ~/.kube/config.
+            config_file: Path to the kube-config file. Defaults to ~/.kube/config.
             context: Set the active context. Defaults to current_context from the kube-config.
-            client_configuration: The kubernetes.client.Configuration to set configs to.
-            persist_config: If True, config file will be updated when changed.
+            client_configuration: Client configuration for cluster authentication.
+                You have to provide valid configuration with Bearer token or
+                with username and password.
+                You can find an example here: https://github.com/kubernetes-client/python/blob/67f9c7a97081b4526470cad53576bc3b71fa6fcc/examples/remote_cluster.py#L31
         """
 
-        self.in_cluster = None
-        if config_file or not utils.is_running_in_k8s():
-            config.load_kube_config(
-                config_file=config_file,
-                context=context,
-                client_configuration=client_configuration,
-                persist_config=persist_config,
-            )
-            self.in_cluster = False
-        else:
-            config.load_incluster_config()
-            self.in_cluster = True
-
-        self.custom_api = client.CustomObjectsApi()
-        self.core_api = client.CoreV1Api()
+        # If client configuration is not set, use kube-config to access Kubernetes APIs.
+        if client_configuration is None:
+            # Load kube-config or in-cluster config.
+            if config_file or not utils.is_running_in_k8s():
+                config.load_kube_config(config_file=config_file, context=context)
+            else:
+                config.load_incluster_config()
+
+        k8s_client = client.ApiClient(client_configuration)
+        self.custom_api = client.CustomObjectsApi(k8s_client)
+        self.core_api = client.CoreV1Api(k8s_client)
         self.api_client = ApiClient()
 
     # ------------------------------------------------------------------------ #