|@is_a@|string|Arvados object type|@["head_uuid","is_a","arvados#collection"]@|
|@exists@|string|Test if a subproperty is present.|@["properties","exists","my_subproperty"]@|
|@is_a@|string|Arvados object type|@["head_uuid","is_a","arvados#collection"]@|
|@exists@|string|Test if a subproperty is present.|@["properties","exists","my_subproperty"]@|