visit

# File activerecord/lib/arel/visitors/dot.rb, line 247
        def visit(o)
          if node = @seen[o.object_id]
            @edge_stack.last.to = node
            return
          end

          node = Node.new(o.class.name, o.object_id)
          @seen[node.id] = node
          @nodes << node
          with_node node do
            super
          end
        end