The attribute [DataType] may not be used on Output parameters.
Instead it is defined on the method if they are [User] methods or [Function] methods inside a class with [FunctionContainer] attribute.
If the method is the [Execution] __Process method the [DataType] attribute is positioned on the [Function] class.
You can also use the provided automatic Code Fix to remove the attribute and put it in the correct place. ( Press Alt + Enter on the Error line to find the Code Fix in the context menu)
Move the attribute to the correct place.
