# File lib/rspec/core/memoized_helpers.rb, line 102
        def self.isolate_for_before_all(example_group_instance)
          example_group_instance.instance_eval do
            @__memoized = BeforeAllMemoizedHash.new(self)

            begin
              yield
            ensure
              @__memoized.preserve_accessed_lets
              @__memoized = nil
            end
          end
        end