added edge selection

src/graph/graph.py

@@ -18,11 +18,20 @@ class Graph:
     def number_of_nodes(self) -> int:
         return len(self.nodes)
     
-    def get_edge_nodes(self, edge) -> tuple[Node, Node]:
+    def get_edge(self, node_1: int, node_2: int) -> int:
+        for edge in self.edges:
+            if (edge.start == node_1 and edge.end == node_2) or (edge.start == node_2 and edge.end == node_1):
+                return self.edges.index(edge)
+        return -1
+    
+    def get_edge_nodes(self, edge: 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)
+    
+    def edge_exists(self, node_1: int, node_2: int) -> bool:
+        return self.get_edge(node_1, node_2) != -1
 
     def dijkstra(self, source_index: int, target_index: int) -> Optional[list[int]]:
         n = len(self.nodes)