Document some of the input graph attributes
Document some of the input graph attributes

shelsonjava/dagre,cpettitt/dagre,GerHobbelt/dagre,abduld/dagre,shelsonjava/dagre,witcxc/dagre,lmcorbo/dagre,lmcorbo/dagre,9n/dagre,lmcorbo/dagre,GerHobbelt/dagre,rwl/dagre,kdawes/dagre,witcxc/dagre,kdawes/dagre,tylingsoft/dagre-layout,cpettitt/dagre,abduld/dagre,9n/dagre,shelsonjava/dagre,GerHobbelt/dagre,9n/dagre,tylingsoft/dagre-layout,kdawes/dagre,abduld/dagre,cpettitt/dagre