Create a "main part" in the script

Because we are going to add a function and we will need to import
`edgelist_to_Graphviz`.

Overlap/Analysis/edgelist_to_Graphviz.py

 #!/usr/bin/env python3
 
-import csv
-import sys
-from os import path
+if __name__ == "__main__":
+    import csv
+    import sys
+    from os import path
 
-import pygraphviz as pgv
+    import pygraphviz as pgv
 
-import report_graph
+    import report_graph
 
-if len(sys.argv) != 3:
-    sys.exit("Required arguments: input-edgelist output-Graphviz")
+    if len(sys.argv) != 3:
+        sys.exit("Required arguments: input-edgelist output-Graphviz")
 
-dir_edgelist = path.dirname(sys.argv[1])
-fname = path.join(dir_edgelist, "e_overestim.txt")
-with open(fname) as f_obj: e_overestim = int(f_obj.read())
-G = pgv.AGraph(directed = True)
+    dir_edgelist = path.dirname(sys.argv[1])
+    fname = path.join(dir_edgelist, "e_overestim.txt")
+    with open(fname) as f_obj: e_overestim = int(f_obj.read())
+    G = pgv.AGraph(directed = True)
 
-with open(sys.argv[1], newline = '') as f:
-    reader = csv.reader(f, delimiter = " ", skipinitialspace = True)
-    for row in reader: G.add_edge(*row)
+    with open(sys.argv[1], newline = '') as f:
+        reader = csv.reader(f, delimiter = " ", skipinitialspace = True)
+        for row in reader: G.add_edge(*row)
 
-report_graph.partition_graph_date(G, e_overestim)
-G.write(sys.argv[2])
+    report_graph.partition_graph_date(G, e_overestim)
+    G.write(sys.argv[2])