add.undirected.edge: Add undirected edge to a 'bnlearn' object.
In rjbgoudie/parental: Light-weight graph package

Adding undirected edges is not an exported function in bnlearn, so this function exposes this functionality.

1 2	add.undirected.edge(x, from, to, check.cycles, update = T, debug = F)

`x`	A 'bnlearn' object, of class `bn`.
`from`	A character string, the label of a node.
`to`	A character string, the label of a node.
`check.cycles`	a boolean value. If TRUE the graph is tested for acyclicity; otherwise the graph is returned anyway.
`update`	A logical
`debug`	a boolean value. If TRUE a lot of debugging output is printed; otherwise the function is completely silent.