reactor-core/src/main/java/reactor/core/publisher/Flux.java
public final Mono<Boolean> hasElement(T value) {
		Objects.requireNonNull(value, "value");
		return any(t -> Objects.equals(value, t));
	}
public final Mono<Boolean> hasElement(T value) {
		Objects.requireNonNull(value, "value");
		return any(t -> Objects.equals(value, t));
	}
Emit a single boolean true if any of the elements of this {@link Flux} sequence is
equal to the provided value.
<p>
The implementation uses short-circuit logic and completes with true if
an element matches the value.

<p>
<img class="marble" src="doc-files/marbles/hasElementForFlux.svg" alt="">

@param value constant compared to incoming signals

@return a new {@link Flux} with <code>true</code> if any element is equal to a given value and <code>false</code>
otherwise