# File lib/bundler/vendor/molinillo/lib/molinillo/dependency_graph.rb, line 146
    def add_child_vertex(name, payload, parent_names, requirement)
      root = !parent_names.delete(nil) { true }
      vertex = add_vertex(name, payload, root)
      vertex.explicit_requirements << requirement if root
      parent_names.each do |parent_name|
        parent_vertex = vertex_named(parent_name)
        add_edge(parent_vertex, vertex, requirement)
      end
      vertex
    end