working progress, need to revise the function to write trees and simulate segregating sites data, node containers contain internal nodes that are not necessary for the newick representation, should skip them, function should split into cases, for local nonlocal nodes, local nodes: internal nodes, tip nodes; internal nodes: cusual for the newick format, or not necessary; tip nodes: actual tip nodes, or tip nodes that is not local, (should draw a venn diagram first to think about the cases) ... for segregating site, only focus on the local tree nodes, verify the branches above internal nodes do not make difference when simulation is undertaken