-* Add existing ArvadosFile or Subcollection to a collection:
-
-```{r}
-folder <- Subcollection$new("src")
-file <- ArvadosFile$new("main.cpp")
-folder$add(file)
-```
-
-```{r}
-collection$add(folder, "cpp")
-```
-
-This examples will add file "main.cpp" in "./cpp/src/" folder if folder exists.
-If subcollection contains more files or folders they will be added recursively.
-