public String getNext(final Random random, final Faker faker) {
        return valueFunction.apply(random, faker);
    }
@return The next value for this field from the value supplier.
The value supplier may either be stateful, i.e. the next value is
dependant on values that cam before it or stateless, i.e. the next
value has no relation to previous values.
stroom-test-common/src/main/java/stroom/test/common/data/Field.java