Resolved some warnings and style issues

marl_factory_grid/environment/groups/objects.py

@@ -1,15 +1,15 @@
 from collections import defaultdict
-from typing import List
+from typing import List, Iterator, Union
 
 import numpy as np
 
-from marl_factory_grid.environment.entity.object import _Object
+from marl_factory_grid.environment.entity.object import Object
 import marl_factory_grid.environment.constants as c
 from marl_factory_grid.utils import helpers as h
 
 
-class _Objects:
-    _entity = _Object
+class Objects:
+    _entity = Object
 
     @property
     def var_can_be_bound(self):
@@ -50,7 +50,7 @@ class _Objects:
     def __len__(self):
         return len(self._data)
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[Union[Object, None]]:
         return iter(self.values())
 
     def add_item(self, item: _entity):
@@ -130,13 +130,14 @@ class _Objects:
         repr_dict = {key: val for key, val in self._data.items() if key not in [c.WALLS]}
         return f'{self.__class__.__name__}[{repr_dict}]'
 
-    def notify_del_entity(self, entity: _Object):
+    def notify_del_entity(self, entity: Object):
         try:
+            # noinspection PyUnresolvedReferences
             self.pos_dict[entity.pos].remove(entity)
         except (AttributeError, ValueError, IndexError):
             pass
 
-    def notify_add_entity(self, entity: _Object):
+    def notify_add_entity(self, entity: Object):
         try:
             if self not in entity.observers:
                 entity.add_observer(self)