Resolve more mypy errors. (#811)

* Redefined variables for type security.

* Redefined variables in `_get_segments` for type safety.

* Delete unnecessary `Union`.

Lib/fontParts/base/contour.py

@@ -8,6 +8,7 @@
     List,
     Optional,
     Tuple,
+    Type,
     TypeVar,
     Union,
 )
@@ -65,8 +66,8 @@ class BaseContour(
 
     """
 
-    segmentClass = None
-    bPointClass = None
+    segmentClass: Optional[Type[BaseSegment]] = None
+    bPointClass: Optional[Type[BaseBPoint]] = None
 
     def _reprContents(self) -> List[str]:
         contents = []
@@ -935,10 +936,10 @@ def _get_segments(self) -> Tuple[BaseSegment, ...]:
         for points in segments:
             if self.segmentClass is None:
                 raise TypeError("segmentClass cannot be None.")
-            segment = self.segmentClass()
-            segment._setPoints(points)
-            self._setContourInSegment(segment)
-            wrapped.append(segment)
+            pointSegment = self.segmentClass()
+            pointSegment._setPoints(points)
+            self._setContourInSegment(pointSegment)
+            wrapped.append(pointSegment)
         return tuple(wrapped)
 
     def __getitem__(self, index: int) -> BaseSegment: