Allow passing in ids for graph files

This will make the file name more informative by having the item id in
the file name, instead of just counting up the number for each graph.

See realrate/RealRate-Private#190.

causing/graph.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 """Create direct, total and mediation Graphviz graph from dot_str using pydot."""
 
-from typing import Dict
+from typing import Dict, Sequence, Optional
 from itertools import chain
 import numpy as np
 from numpy import amax, array_equal, allclose, isnan, logical_and
@@ -210,6 +210,7 @@ def create_graphs(
     node_name,
     show_nr_indiv,
     final_var_in_percent=False,
+    ids: Optional[Sequence[str]] = None,
 ):
     """creates direct, total and mediation graph,
     for theoretical model and estimated model"""
@@ -253,13 +254,18 @@ def make_graph(filename, x_weights_idmat_nodeff, y_weights_idmat_nodeff, **kwarg
     print()
 
     for i in range(min(show_nr_indiv, len(graph_json["mx_indivs"]))):
+        if ids:
+            item_id = ids[i]
+        else:
+            item_id = str(i)
+
         # compute color base for each individual separately
         # using _indiv quantities based on _theo quantities times absolute deviation from median
         print("Generate graphs for individual {:5}".format(i))
 
         # IDE
         direct_indiv_graph = make_graph(
-            "IDE" + "_" + str(i),
+            f"IDE_{item_id}",
             (graph_json["mx_indivs"][i], None),
             (graph_json["my_indivs"][i], None),
             color=True,
@@ -268,7 +274,7 @@ def make_graph(filename, x_weights_idmat_nodeff, y_weights_idmat_nodeff, **kwarg
 
         # IME
         mediation_indiv_graph = make_graph(
-            "IME" + "_" + str(i),
+            f"IME_{item_id}",
             (graph_json["eyx_indivs"][i], np.array(graph_json["exj_indivs"])[:, i]),
             (graph_json["eyy_indivs"][i], np.array(graph_json["eyj_indivs"])[:, i]),
             color=True,
@@ -278,7 +284,7 @@ def make_graph(filename, x_weights_idmat_nodeff, y_weights_idmat_nodeff, **kwarg
 
         # ITE
         total_indiv_graph = make_graph(
-            "ITE" + "_" + str(i),
+            f"ITE_{item_id}",
             (graph_json["ex_indivs"][i], None),
             (graph_json["ey_indivs"][i], None),
             color=True,