public <R> StreamEx<R> mapKeyValue(BiFunction<? super K, ? super V, ? extends R> mapper) {
        return this.<R> map(toFunction(mapper));
    }
public < R > StreamEx < R > mapKeyValue ( BiFunction < ? super K , ? super V , ? extends R > mapper ) { return this . < R > map ( toFunction ( mapper ) ) ; }
Returns a {@link StreamEx} consisting of the results of applying the
given function to the keys and values of this stream.

<p>
This is an <a href="package-summary.html#StreamOps">intermediate</a>
operation.

@param <R> The element type of the new stream
@param mapper a <a
href="package-summary.html#NonInterference">non-interfering </a>,
<a href="package-summary.html#Statelessness">stateless</a> function to apply to key and
value of each {@link Entry} in this stream
@return the new stream