Represents a leaf in an {S3::Tree}.
When enumerating nodes in an S3 tree, keys are yielded as leaf nodes (they have no children beneath them).
@see Tree @note Generally you do not need to create leaf nodes
@api private
@return [false]
@return [String] the key this leaf node represents.
@return [true]
@return [S3Object] The object this leaf node represents.
@return [MultipartUpload] Returns the object version this leaf
node represents.
@return [ObjectVersion] Returns the object version this leaf
[Validate]