Add weighted edges and self loop edges to graphs

manim/mobject/geometry/line.py

@@ -65,8 +65,8 @@ def set_points_by_ends(
         self,
         start: Point3D | Mobject,
         end: Point3D | Mobject,
-        buff: float = 0,
-        path_arc: float = 0,
+        buff: float = None,  # 0   #?Why default value to 0? Shouldn't be `self.buff` instead?
+        path_arc: float = None,  # 0   #?Why default value to 0? Shouldn't be `self.buff` instead?
     ) -> None:
         """Sets the points of the line based on its start and end points.
         Unlike :meth:`put_start_and_end_on`, this method respects `self.buff` and
@@ -83,6 +83,11 @@ def set_points_by_ends(
         path_arc
             The angle of a circle spanned by this arc, by default 0 which is a straight line.
         """
+        if buff is None:
+            buff = self.buff
+        if path_arc is None:
+            path_arc = self.path_arc
+
         self._set_start_and_end_attrs(start, end)
         if path_arc:
             arc = ArcBetweenPoints(self.start, self.end, angle=self.path_arc)