main: fixed error with comma separator

Before this patch, there was the `ValueError` on getting the node name
when the input file used comma separator instead of colon, i.e.:

```
AggregateExec, mode=Partial, gby=[], aggr=[COUNT(*)], metrics=[output_rows=32, elapsed_compute=113.653569ms]
```

This patch allows to work with any separator.

Resolves #2

main.py

@@ -25,17 +25,16 @@
 
 if __name__ == "__main__":
 
-
     nodes = dict()
     with open(args.input_file, 'r') as f:
         source = f.readlines()
 
     INDEX_TO_LEVEL = generate_index_to_level_dict(source)
 
     for i in range(len(INDEX_TO_LEVEL)):
-        name, content_raw = source[i].strip().split(':', 1)
+        name, content_raw = source[i].strip().split(' ', 1)
         content = (i, INDEX_TO_LEVEL[i])
-        node = Node(i, name, content_raw)
+        node = Node(i, name[0:-1], content_raw)
         nodes.update({i: node})
         if i == 0:
             continue