# File lib/puppet/simple_graph.rb, line 227
227:     def remove_vertex!(vertex)
228:         return nil unless vertex?(vertex)
229:         @vertices[vertex].edges.each { |edge| remove_edge!(edge) }
230:         @edges -= @vertices[vertex].edges
231:         @vertices[vertex].clear
232:         @vertices.delete(vertex)
233:     end