Function builtin_class 

fn builtin_class(
    args: &[RValue],
    _: &[(String, RValue)],
) -> Result<RValue, RError>

Get the class of an object.

Returns the explicit class attribute if set, otherwise the implicit class based on the object’s type (e.g., “numeric”, “character”, “list”).

@param x object to inspect @return character vector of class names