code: function isMounted() {
        if (false) {
          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