code: function() {
        if (process.env.NODE_ENV !== 'production') {
          warning(
            this.__didWarnIsMounted,
            '%s: isMounted is deprecated. Instead, make sure to clean up ' +
              'subscriptions and pending requests in componentWillUnmount to ' +
              'prevent memory leaks.',
            (this.constructor && this.constructor.displayName) ||
              this.name ||
              'Component'
          );
          this.__didWarnIsMounted = true;
        }
        return !!this.__isMounted;
      }
docs: Checks whether or not this composite component is mounted.
  @return {boolean} True if mounted, false otherwise.
  @protected
  @final