This class is created internally by {@see \Google\Cloud\Vision\Annotation} and is used to represent various
annotation feature results.
This class should not be instantiated externally.
Entities are returned by {@see \Google\Cloud\Vision\Annotation::landmarks()},
{@see \Google\Cloud\Vision\Annotation::logos()},
{@see \Google\Cloud\Vision\Annotation::labels()} and
{@see \Google\Cloud\Vision\Annotation::text()}.