def activate(span:, finish_on_close: true)
      return active if active && active.span == span
      LightStep::Scope.new(manager: self, span: span, finish_on_close: finish_on_close).tap do |scope|
        add_scope(scope)
      end
    end
def activate(span:, finish_on_close: true)
      return active if active && active.span == span
      LightStep::Scope.new(manager: self, span: span, finish_on_close: finish_on_close).tap do |scope|
        add_scope(scope)
      end
    end
Make a span instance active.

 @param span [Span] the Span that should become active
 @param finish_on_close [Boolean] whether the Span should automatically be
   finished when Scope#close is called
 @return [Scope] instance to control the end of the active period for the
  Span. It is a programming error to neglect to call Scope#close on the
  returned instance.