Package author: Jukka Aho (@ahojukka5)

The need to determine pseudoperipheral vertices arises from several graph-theoretical approaches for ordering sparse matrix equations. This package implements George-Liu algorithm for finding a pseudoperipheral vertex in a graph aiming at returning a vertex having a large eccentricity.

Let's consider the following graph:

It is easy to see that peripheral vertices for this graph are 9 and 6. The
requirement for the description of the graph is the following: graph must
implement `getindex`

and each adjacency list must be iterable. For example, list
of lists or dictionary of lists meets the requirements.

```
G = Dict(
1 => (3, 8, 9),
2 => (3, 8, 7),
3 => (1, 2),
4 => (8, 9),
5 => (7, 8),
6 => (2, 7),
7 => (5, 2, 6),
8 => (1, 2, 4, 5),
9 => (1, 4))
```

Starting from node 1:

```
w0 = 1
w1 = find(G, w0)
w2 = find(G, w1)
w3 = find(G, w2)
println(w1)
println(w2)
println(w3)
# output
6
9
6
```

Any contributions are highly appreciated! If you have some good ideas how to make this package better, feel free to open an issue or send me an email.