diff --git a/pddl/logic/effects.py b/pddl/logic/effects.py
index 140f1d4..70087f6 100644
--- a/pddl/logic/effects.py
+++ b/pddl/logic/effects.py
@@ -12,7 +12,7 @@
 
 """This modules implements PDDL effects."""
 import functools
-from typing import AbstractSet, Collection, Optional, TypeVar, Union
+from typing import AbstractSet, Collection, Optional, Union
 
 from pddl.helpers.base import _typed_parameters, ensure_set
 from pddl.helpers.cache_hash import cache_hash
@@ -20,8 +20,6 @@
 from pddl.logic.base import And, Atomic, Formula, Not, OneOf
 from pddl.parser.symbols import Symbols
 
-EffectType = TypeVar("EffectType")
-
 
 @cache_hash
 @functools.total_ordering