class Rspec::Core::ExampleGroup

def self.describe(*args, &example_group_block)
  @_subclass_count ||= 0
  @_subclass_count += 1
  args << {} unless args.last.is_a?(Hash)
  args.last.update(:example_group_block => example_group_block)
  args.last.update(:caller => caller)
  args.unshift Rspec.configuration unless args.first.is_a?(Rspec::Core::Configuration)
  const_set(
    "Nested_#{@_subclass_count}",
    subclass(self, args, &example_group_block)
  )
end