just return the keys instead of all the processors in maps_utils,py

Author: r41k0u

pythonbpf/maps/maps_utils.py

@@ -37,4 +37,4 @@ def get_processor(cls, map_type_name):
     @classmethod
     def known_types(cls):
         """Names of every registered map type, for error messages"""
-        return list(cls._processors)
+        return list(cls._processors.keys())