Objects from the Class
Objects can be created by calls of the form new("undirectedEdge", ...)
which admit short-hands of the form u(...).Extends
Class "edge", directly.
Class "integer", from data part.
Class "vector", by class "integer".
Class "numeric", by class "integer".Warning
The constructor will try to handle any vector input
by silently transforming it into a list of strictly positive integers.