private function get_license_ids_associated_with_installs() {
            if ( ! $this->_is_network_active ) {
                if ( ! is_object( $this->_site ) ||
                     ! FS_Plugin_License::is_valid_id( $this->_site->license_id )
                ) {
                    return array();
                }

                return array( $this->_site->license_id );
            }

            $license_ids = array();
            $sites       = self::get_sites();
            foreach ( $sites as $site ) {
                $blog_id = self::get_site_blog_id( $site );
                $install = $this->get_install_by_blog_id( $blog_id );

                if ( ! is_object( $install ) ||
                     ! FS_Plugin_License::is_valid_id( $install->license_id )
                ) {
                    continue;
                }

                $license_ids[ $install->license_id ] = true;
            }

            return array_keys( $license_ids );
        }