# File lib/puppet/simple_graph.rb, line 223
223:   def remove_vertex!(vertex)
224:     return nil unless vertex?(vertex)
225:     @vertices[vertex].edges.each { |edge| remove_edge!(edge) }
226:     @edges -= @vertices[vertex].edges
227:     @vertices[vertex].clear
228:     @vertices.delete(vertex)
229:   end