default SpeedmentPredicate<ENTITY> isNotEmpty() {
        return isEmpty().negate();
    }
Returns a {@link java.util.function.Predicate} that will evaluate to
{@code true}, if and only if this Field <em>is not empty</em>. An empty
Field contains a String with length zero.

@return a Predicate that will evaluate to {@code true}, if and only if
this Field <em>is not empty</em>

@see String#isEmpty()
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/trait/HasStringOperators.java