code: def activate(self, span, finish_on_close):
          
          scope = _ThreadLocalScope(self, span, finish_on_close)
          setattr(self._tls_scope, 'active', scope)
          return scope
docs: Make a :class:`~opentracing.Span` instance active.
  
          :param span: the :class:`~opentracing.Span` that should become active.
          :param finish_on_close: whether *span* should automatically be
              finished when :meth:`Scope.close()` is called.
  
          :return: a :class:`~opentracing.Scope` instance to control the end
              of the active period for the :class:`~opentracing.Span`.
              It is a programming error to neglect to call :meth:`Scope.close()`
              on the returned instance.