Takes a PCollection<V> and produces a PCollection<KV<K, V>> by associating each input element with a key.

There are two versions of WithKeys, depending on how the key should be determined:

• WithKeys.of(SerializableFunction<V, K> fn) takes a function to compute the key from each value.
• WithKeys.of(K key) associates each value with the specified key.

Examples

• Keys for extracting the key of each component.
• Values for extracting the value of each element.
• KvSwap swaps key-value pair values.