default StringProperty typeMapperProperty() {
        return stringPropertyOf(TYPE_MAPPER, 
            () -> HasTypeMapper.super.getTypeMapper().orElse(null)
        );
    }
A trait for documents that have a {@code TypeMapper} specified. This 
corresponds to the {@link HasTypeMapper} trait but for observable documents.

@author Emil Forslund
@since  3.0.2
tool-parent/tool-config/src/main/java/com/speedment/tool/config/trait/HasTypeMapperProperty.java