Generic method for calculating the degree of a list of nodes in a
"dbn" S3 object. Calls bnlearn's degree
underneath.
The degree function is specifically coded to look for either the "bn"
or the "bn.fit" method inside bnlearn, so I have to cast the "dbn" class
into "bn" for it to work.
# S3 method for dbn
degree(object, Nodes, ...)
the degree of the nodes
a "dbn" object
which nodes to check
additional parameters