set n_threads in GPT4All python bindings (#1042)

* set n_threads in GPT4All

* changed default n_threads to None

gpt4all-bindings/python/gpt4all/gpt4all.py

@@ -22,7 +22,7 @@ class GPT4All():
         model: Pointer to underlying C model.
     """
 
-    def __init__(self, model_name: str, model_path: str = None, model_type: str = None, allow_download = True):
+    def __init__(self, model_name: str, model_path: str = None, model_type: str = None, allow_download = True, n_threads = None):
         """
         Constructor
 
@@ -33,12 +33,16 @@ class GPT4All():
             model_type: Model architecture. This argument currently does not have any functionality and is just used as
                 descriptive identifier for user. Default is None.
             allow_download: Allow API to download models from gpt4all.io. Default is True. 
+            n_threads: number of CPU threads used by GPT4All. Default is None, than the number of threads are determined automatically.
         """
         self.model_type = model_type
         self.model = pyllmodel.LLModel()
         # Retrieve model and download if allowed
         model_dest = self.retrieve_model(model_name, model_path=model_path, allow_download=allow_download)
         self.model.load_model(model_dest)
+        # Set n_threads
+        if n_threads != None:
+            self.model.set_thread_count(n_threads)
 
     @staticmethod
     def list_models():