Improve segment.py. (#783)

* Minor documentation improvements.

---------

Co-authored-by: knutnergaard <knutnergaard@users.noreply.github.com>

Lib/fontParts/base/segment.py

@@ -450,8 +450,8 @@ def _iterPoints(self, **kwargs: Any) -> Generator[BasePoint]:
 
         This is the environment implementation of :meth:`BaseSegment.__iter__`.
 
-        :return: An iterator over the :class:`BasePoint` instances belonging to
-            the segment.
+        :return: An iterator over the :class:`BasePoint` subclass instances
+            belonging to the segment.
 
         .. note::
 
@@ -481,7 +481,7 @@ def _len(self, **kwargs: Any) -> int:
         This is the environment implementation of :meth:`BaseSegment.__len__`.
 
         :return: An :class:`int` representing the number of :class:`BasePoint`
-            instances belonging to the segment.
+            subclass instances belonging to the segment.
 
         .. note::
 
@@ -496,7 +496,7 @@ def _len(self, **kwargs: Any) -> int:
 
         This attribute is read-only.
 
-        :return: A :class:`tuple` of :class`BasePoints`.
+        :return: A :class:`tuple` of :class`BasePoint` instances.
 
         """,
     )