updated docstring and changed name from _hierarchy_pos to _tree_layout
updated docstring and changed name from _hierarchy_pos to _tree_layout

iModels/mbuild,ctk3b/mbuild,summeraz/mbuild,Jonestj1/mbuild,tcmoore3/mbuild,sallai/mbuild,summeraz/mbuild,sallai/mbuild,ctk3b/mbuild,Jonestj1/mbuild,tcmoore3/mbuild,iModels/mbuild