add utility function to split its graph in G and H graph

fgutils/utils.py

@@ -54,3 +54,20 @@ def add_implicit_hydrogens(graph: nx.Graph) -> nx.Graph:
             graph.add_node(h_id, symbol="H")
             graph.add_edge(n_id, h_id, bond=1)
     return graph
+
+
+def split_its(graph: nx.Graph) -> tuple[nx.Graph, nx.Graph]:
+    def _set_rc_edge(g, u, v, b):
+        if b == 0:
+            g.remove_edge(u, v)
+        else:
+            g[u][v]["bond"] = b
+
+    g = graph.copy()
+    h = graph.copy()
+    for u, v, d in graph.edges(data=True):
+        bond = d["bond"]
+        if isinstance(bond, tuple):
+            _set_rc_edge(g, u, v, bond[0])
+            _set_rc_edge(h, u, v, bond[1])
+    return g, h

test/test_utils.py

@@ -1,5 +1,7 @@
 from fgutils.parse import parse
-from fgutils.utils import add_implicit_hydrogens
+from fgutils.utils import add_implicit_hydrogens, split_its
+
+from .test_parse import _assert_graph
 
 
 def _assert_Hs(graph, idx, h_cnt):
@@ -103,4 +105,33 @@ def test_tin_tetrachloride():
     _assert_Hs(graph, 4, 0)
 
 
-# SeO2 SnCL4
+def test_split_its():
+    its = parse("C1<2,>C<,2>C<2,>C(C)<0,1>C<2,>C(C(=O)O)<0,1>1")
+    exp_nodes = {i: "C" for i in range(10)}
+    exp_nodes[8] = "O"
+    exp_nodes[9] = "O"
+    exp_edges_g = [
+        (0, 1, 2),
+        (1, 2, 1),
+        (2, 3, 2),
+        (3, 4, 1),
+        (5, 6, 2),
+        (6, 7, 1),
+        (7, 8, 2),
+        (7, 9, 1),
+    ]
+    exp_edges_h = [
+        (0, 1, 1),
+        (0, 6, 1),
+        (1, 2, 2),
+        (2, 3, 1),
+        (3, 4, 1),
+        (3, 5, 1),
+        (5, 6, 1),
+        (6, 7, 1),
+        (7, 8, 2),
+        (7, 9, 1),
+    ]
+    g, h = split_its(its)
+    _assert_graph(g, exp_nodes, exp_edges_g)
+    _assert_graph(h, exp_nodes, exp_edges_h)