Update graph_utilities.py

Start adding code

swmmanywhere/graph_utilities.py

@@ -13,7 +13,7 @@
 from heapq import heappop, heappush
 from itertools import product
 from pathlib import Path
-from typing import Any, Callable, Dict, Hashable, List, Optional
+from typing import Any, Callable, Dict, Hashable, List, Optional, cast
 
 import geopandas as gpd
 import networkx as nx
@@ -220,6 +220,33 @@ def __call__(self,
         for u, v, key in edges_to_remove:
             G.remove_edge(u, v, key)
         return G
+
+@register_graphfcn
+def remove_parallels(G: nx.MultiDiGraph, weight = 'length') -> nx.DiGraph:
+    """Remove parallel edges from a street network.
+
+    Retain the edge with the smallest weight (i.e., length).
+
+    Args:
+        G (nx.MultiDiGraph): A graph.
+        weight (str): The edge attribute to use as the weight.
+    
+    Returns:
+        G (nx.DiGraph): The graph with parallel edges removed.
+
+    Author:
+        Taher Chegini
+    """
+    graph = ox.get_digraph(G)
+    _, _, attr_list = next(iter(graph.edges(data=True)))  # type: ignore
+    attr_list = cast("dict[str, Any]", attr_list)
+    if weight not in attr_list:
+        raise ValueError(f"{weight} not in edge attributes.")
+    attr = nx.get_node_attributes(graph, weight)
+    parallels = (e for e in attr if e[::-1] in attr)
+    graph.remove_edges_from({e if attr[e] > attr[e[::-1]] 
+                             else e[::-1] for e in parallels})
+    return graph
 
 @register_graphfcn
 class format_osmnx_lanes(BaseGraphFunction,