Writes out the RDS tree in NetDraw format
write.netdraw(x, file = NULL, by.seed = FALSE)
An rds.data.frame.
a character vector representing a file.
If true, seperate files will be created for each seed.
If by.seed is false, two files are created using 'file' as a base name.
paste0(file,".DL")
contains the edge information, and paste0(file,".vna")
contains the nodal attributes