code: @Nonnull
      public <B> HashTable<K, B> toHashTable(@Nonnull F<ImmutableList<V>, B> conversion) {
          //return this.data.foldLeft((acc, p) -> acc.put(p.a, conversion.apply(p.b)), HashTable.empty(this.data.hasher));
          return this.toHashTable((k, vs) -> conversion.apply(vs));
      }
docs: version: key is irrelevant