Added edge creation and rendering

src/graph/graph.py

@@ -15,6 +15,12 @@ class Graph:
     def add_edge(self, start_index: int, end_index: int, length: float) -> None:
         self.edges.append(Edge(start_index, end_index, length))
 
+    def number_of_nodes(self) -> int:
+        return len(self.nodes)
+    
+    def get_edge_nodes(self, edge) -> tuple[Node, Node]:
+        return self.nodes[edge.start], self.nodes[edge.end]
+
     def edges_adjacent_to(self, node_i: int) -> Iterator[Edge]:
         return filter(lambda e: e.start == node_i or e.end == node_i, self.edges)