Returning a class - Object Oriented Programming Design Patterns

I'm trying to build a ETL-type module in scala for Spark. I have a base class transformer,

trait transformer{
  def transformer()
}

However then I extend this base class to two more types single return and multi return,

trait UnaryReturnTransformer extends transformer{
def inPorts()
def outPorts()
def setExpressions()
}

trait MultiReturnTransformer extends transformer{
def inPorts()
def outPorts()
def setExpressions()
}

Now, the actual implementation say, lookup transformer,

class LookupTransformer extends UnaryReturnTransformer{
//set local variables
//override functions
override def inports(df:DataFrane):

}

Is it better to return the class itself so that we could chain the code, Eg,

new LookupTransformer().inports().setExpression().transform().Outports()

or make them as

val x=new LookupTransformer()
x.inports()
x.setExpression()
x.transform()
val ret=x.outPorts()

This seems more like a design question to me and It would be great to know what is the best practice to design such a system.

Thanks!