A cograph_network with the new nodes appended (isolated until
edges are added), or the input format when keep_format = TRUE.
Arguments
x
Network input.
labels
Character vector of labels for the new nodes.
...
Named vectors of node attributes for the new nodes, each of
length 1 (recycled) or length(labels). Columns the network does not
already have are created and filled with NA for the existing nodes.