[igraph] igraph output header

[Jey Narasimhan]

Hi,

Why is some times python-igraph prints different summary information?
I tried two undirected weighted graphs, and found the header to be
different:

First graph:

IGRAPH U-W- 4 5 --
+ attr: b (v), frog (v), g (v), id (v), indegree (v), label (v), r (v), size
  (v), url (v), x (v), y (v), Edge Id (e), Edge Label (e), weight (e)
+ edges:
0--1 0--2 0--3 0--1 1--2

Second graph:
IGRAPH UNW- 3 3 --
+ attr: id (v), name (v), day (e), mon (e), sec (e), wd (e), weight (e), year
  (e)
+ edges (vertex names):
9141.0--4693.0, 9141.0--19450.0, 9141.0--19450.0

What is the difference between U-W and UNW in the header?

Thanks.