Function interp_valid_object 

fn interp_valid_object(
    args: &[RValue],
    _named: &[(String, RValue)],
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Validate an S4 object.

Runs the validity function registered for the object’s class, if any.

@param object an S4 object @return the object if valid, error otherwise