clean() {
            for(let k in this.map) {
                if(this.map.hasOwnProperty(k)) {
                    if(this.map[k].length <= 0) {
                        delete this.map[k];
                    }
                }
            }
        }
/**
         * Removes all keys associated with empty lists from the HashMap.
         */
Removes all keys associated with empty lists from the HashMap.
Removes all keys associated with empty lists from the HashMap .
clean() {
            for(let k in this.map) {
                if(this.map.hasOwnProperty(k)) {
                    if(this.map[k].length <= 0) {
                        delete this.map[k];
                    }
                }
            }
        }
clean ( ) { for ( let k in this . map ) { if ( this . map . hasOwnProperty ( k ) ) { if ( this . map [ k ] . length <= 0 ) { delete this . map [ k ] ; } } } }
Removes all keys associated with empty lists from the HashMap.
Removes all keys associated with empty lists from the HashMap .