fix: xformers use importlib

modules/import_hook.py

-import builtins
 import sys
 
-old_import = builtins.__import__
-IMPORT_BLACKLIST = []
-
 
 if "xformers" not in "".join(sys.argv):
-    IMPORT_BLACKLIST.append("xformers")
-
-
-def import_hook(*args, **kwargs):
-    if args[0] in IMPORT_BLACKLIST:
-        raise ImportError("Import of %s is blacklisted" % args[0])
-    return old_import(*args, **kwargs)
-
-
-builtins.__import__ = import_hook
+    sys.modules["xformers"] = None