update serving API

transformers/commands/serving.py

@@ -24,7 +24,11 @@ def serve_command_factory(args: Namespace):
     Factory function used to instantiate serving server from provided command line arguments.
     :return: ServeCommand
     """
-    nlp = pipeline(task=args.task, model=args.model, config=args.config, tokenizer=args.tokenizer, device=args.device)
+    nlp = pipeline(task=args.task,
+                   model=args.model if args.model else None,
+                   config=args.config,
+                   tokenizer=args.tokenizer,
+                   device=args.device)
     return ServeCommand(nlp, args.host, args.port)
 
 
@@ -68,12 +72,12 @@ class ServeCommand(BaseTransformersCLICommand):
         """
         serve_parser = parser.add_parser('serve', help='CLI tool to run inference requests through REST and GraphQL endpoints.')
         serve_parser.add_argument('--task', type=str, choices=SUPPORTED_TASKS.keys(), help='The task to run the pipeline on')
-        serve_parser.add_argument('--device', type=int, default=-1, help='Indicate the device to run onto, -1 indicates CPU, >= 0 indicates GPU (default: -1)')
         serve_parser.add_argument('--host', type=str, default='localhost', help='Interface the server will listen on.')
         serve_parser.add_argument('--port', type=int, default=8888, help='Port the serving will listen to.')
-        serve_parser.add_argument('--model', type=str, required=True, help='Model\'s name or path to stored model.')
+        serve_parser.add_argument('--model', type=str, help='Model\'s name or path to stored model.')
         serve_parser.add_argument('--config', type=str, help='Model\'s config name or path to stored model.')
         serve_parser.add_argument('--tokenizer', type=str, help='Tokenizer name to use.')
+        serve_parser.add_argument('--device', type=int, default=-1, help='Indicate the device to run onto, -1 indicates CPU, >= 0 indicates GPU (default: -1)')
         serve_parser.set_defaults(func=serve_command_factory)
 
     def __init__(self, pipeline: Pipeline, host: str, port: int):