Write `e_overestim` to the graph-tool file

So we can use the output file of `extract_component.py` as input of
`draw_segments.py`, for example.

Overlap/extract_component.py

@@ -11,6 +11,7 @@ each vertex of the graph.
 import csv
 import pathlib
 import sys
+from os import path
 
 import graph_tool
 from graph_tool import topology
@@ -32,6 +33,12 @@ if input_suffix == ".csv":
                                        hash_type="int",
                                        csv_options = {'delimiter': ' ',
                                                       'skipinitialspace': True})
+    dir_edgelist = path.dirname(sys.argv[1])
+    e_overestim_file = path.join(dir_edgelist, "e_overestim.txt")
+    g.graph_properties["e_overestim"] = g.new_graph_property("int")
+
+    with open(e_overestim_file) as f_obj:
+        g.graph_properties["e_overestim"] = int(f_obj.read())
 else:
     # assert input_suffix in {".gt", ".graphml"}
     g = graph_tool.load_graph(sys.argv[1])