Fix 4910 kwargs

src/datasets/arrow_dataset.py

@@ -3065,6 +3065,19 @@ def map(
         if keep_in_memory and cache_file_name is not None:
             raise ValueError("Please use either `keep_in_memory` or `cache_file_name` but not both.")
 
+        # 7756 fix (multiprocessing hang on bad start_method)
+
+        if num_proc and num_proc > 1 :
+            try :
+                import multiprocessing as mp 
+                if mp.get_start_method() not in ['forkserver','spawn'] :
+                    logger.warning ("map(num_proc > 1) may hang. fallback to 1")
+                    num_proc = 1
+
+            except :
+                (ImportError, RuntimeError) :
+                num_proc = 1
+
         if num_proc == 0:
             num_proc = None
         elif num_proc is not None and num_proc < 0:

src/datasets/load.py

@@ -1175,8 +1175,8 @@ def load_dataset_builder(
         features=features,
         token=token,
         storage_options=storage_options,
-        **builder_kwargs,
-        **config_kwargs,
+        **{**builder_kwargs,
+        **config_kwargs},
     )
     builder_instance._use_legacy_cache_dir_if_possible(dataset_module)