@Override
        public final boolean equals(Object o) {
            if (this == o) return true;
            else if (!(o instanceof MapperExpression)) return false;
            final MapperExpression<?, ?, ?> that = (MapperExpression<?, ?, ?>) o;
            return Objects.equals(inner(), that.inner()) &&
                Objects.equals(mapper(), that.mapper()) &&
                Objects.equals(mapperType(), that.mapperType());
        }
Abstract base for a mapping operation.

@param <T>       the input type
@param <INNER>   the inner expression type
@param <MAPPER>  the mapping functional interface
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/internal/expression/MapperUtil.java