fix typo in fixture_types and fix lint issues

tests/fixture_types.py

@@ -52,19 +52,25 @@
 else:
     # Fallback for Python 3.7 and 3.8
     class FixtureDict(Generic[K, V], Dict[K, V]):
+        """
+        This class is necessary to allow FixtureDict to be subscriptable
+        when using it to type hint.
+        """
         pass
 
     class FixtureTuple(Generic[K, V], Tuple[K, V]):
+        """
+        This class is necessary to allow FixtureTuple to be subscriptable
+        when using it to type hint.
+        """
         pass
 
     FixtureBytes = pytest.fixture
     FixtureCallable = pytest.fixture
     FixtureCelery = pytest.fixture
-    FixtureDict = FixtureDict
     FixtureInt = pytest.fixture
     FixtureModification = pytest.fixture
     FixtureNamespace = pytest.fixture
     FixtureRedis = pytest.fixture
     FixtureSignature = pytest.fixture
-    FixtureStr = Fixture
-    FixtureTuple = pytest.fixture
+    FixtureStr = pytest.fixture