@Override
        public FieldIsNotNullPredicate<ENTITY, T> negate() {
            return new MapperIsNotNull<>(expression, field);
        }
Abstract base implementation of {@link FieldMapper}.

@author Emil Forslund
@since  3.1.0
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/internal/expression/AbstractFieldMapper.java