key_for (DataMapper::Sweatshop::UniqueWorker)

    # File lib/dm-sweatshop/unique.rb, line 74
          def self.key_for(&block)
            raise "You need to install ParseTree to use anonymous an anonymous unique (gem install ParseTree). In the mean time, explicitly declare a key: unique(:my_key) { ... }" unless Object::const_defined?("ParseTree")

            klass = Class.new
            name = "tmp"
            klass.send(:define_method, name, &block)
            self.parser ||= ParseTree.new(false)
            self.parser.parse_tree_for_method(klass, name).last
          end