Takes an arbitrary amount of Graphs or PipeOps (or objects that can be automatically
converted into Graphs or PipeOps, see as_graph() and as_pipeop()) as inputs and joins
them in a new Graph.
The PipeOps of the input Graphs are not joined with new edges across
Graphs, so if length(graphs) > 1 the resulting Graph will be disconnected.
length(graphs) > 1
list of (Graph | PipeOp)
List of elements with one of the types defined above, which are the
Graphs to be joined.
Graph the resulting Graph.
Other Graph operators: %>>%,