Fix(graph): Allow any Line subclass as edge_type in Graph/DiGraph (#4251)

* Fix(graph) : fix Line subclass usage for Graph and DiGraph

Fix(graph): LabeledLine can now be used in _add_edge

* Test(test_graph.py): add tests for LabeledLine as edge_type in Graph and DiGraph

Fix(test_graph): Fixed test_graph_accepts_labeledline_as_edge_type() always failing.

Author: Akshat-Mishra-py

manim/mobject/graph.py

@@ -1035,7 +1035,10 @@ def _add_edge(
         self._edge_config[(u, v)] = edge_config
 
         edge_mobject = edge_type(
-            self[u].get_center(), self[v].get_center(), z_index=-1, **edge_config
+            start=self[u].get_center(),
+            end=self[v].get_center(),
+            z_index=-1,
+            **edge_config,
         )
         self.edges[(u, v)] = edge_mobject
 
@@ -1543,8 +1546,8 @@ def _populate_edge_dict(
     ):
         self.edges = {
             (u, v): edge_type(
-                self[u].get_center(),
-                self[v].get_center(),
+                start=self[u].get_center(),
+                end=self[v].get_center(),
                 z_index=-1,
                 **self._edge_config[(u, v)],
             )
@@ -1750,8 +1753,8 @@ def _populate_edge_dict(
     ):
         self.edges = {
             (u, v): edge_type(
-                self[u],
-                self[v],
+                start=self[u],
+                end=self[v],
                 z_index=-1,
                 **self._edge_config[(u, v)],
             )

tests/module/mobject/test_graph.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from manim import DiGraph, Graph, Scene, Text, tempconfig
+from manim import DiGraph, Graph, LabeledLine, Scene, Text, tempconfig
 from manim.mobject.graph import _layouts
 
 
@@ -91,6 +91,29 @@ def test_graph_remove_edges():
     assert set(G.edges.keys()) == set()
 
 
+def test_graph_accepts_labeledline_as_edge_type():
+    vertices = [1, 2, 3, 4]
+    edges = [(1, 2), (2, 3), (3, 4), (4, 1)]
+    edge_config = {
+        (1, 2): {"label": "A"},
+        (2, 3): {"label": "B"},
+        (3, 4): {"label": "C"},
+        (4, 1): {"label": "D"},
+    }
+    G_manual = Graph(vertices, edges, edge_type=LabeledLine, edge_config=edge_config)
+    G_directed = DiGraph(
+        vertices, edges, edge_type=LabeledLine, edge_config=edge_config
+    )
+
+    for _edge_key, edge_obj in G_manual.edges.items():
+        assert isinstance(edge_obj, LabeledLine)
+        assert hasattr(edge_obj, "label")
+
+    for _edge_key, edge_obj in G_directed.edges.items():
+        assert isinstance(edge_obj, LabeledLine)
+        assert hasattr(edge_obj, "label")
+
+
 def test_custom_animation_mobject_list():
     G = Graph([1, 2, 3], [(1, 2), (2, 3)])
     scene = Scene()