fix api of uphost and mark region config is optional (#15)

BUGFIX:

- Mark `region` config is optional
- Update field `CPUSet` at the model `PHostSetSchema`

Author: yufeiminds

ucloud/core/client/_cfg.py

@@ -5,7 +5,7 @@
 
 class ConfigSchema(schema.Schema):
     fields = {
-        "region": fields.Str(required=True),
+        "region": fields.Str(),
         "project_id": fields.Str(),
         "base_url": fields.Str(default="https://api.ucloud.cn"),
         "user_agent": fields.Str(),
@@ -46,7 +46,7 @@ class Config:
 
     def __init__(
         self,
-        region: str,
+        region: str = None,
         project_id: str = None,
         base_url: str = "https://api.ucloud.cn",
         user_agent: str = None,

ucloud/core/client/_client.py

@@ -130,4 +130,4 @@ def _build_user_agent(self) -> str:
         return user_agent
 
     def __repr__(self):
-        return '<{}("{}")>'.format(self.__class__.__name__, self.config.region)
+        return '<{}(region="{}")>'.format(self.__class__.__name__, self.config.region)