func (s *stageImpl) OutgoingSchema() sif.Schema {
	return s.outgoingSchema
}
OutgoingSchema is the Schema for data leaving this Stage
package dataframe
import (
	"github.com/go-sif/sif"
)
type stageImpl struct {
	id             int
	incomingSchema sif.Schema
	outgoingSchema sif.Schema
	frames         []*dataFrameImpl
}
func createStage(nextID int) *stageImpl {
	s := &stageImpl{
		id:             nextID,
		incomingSchema: nil,
		outgoingSchema: nil,
		frames:         []*dataFrameImpl{},
	}
	return s
}
func (s *stageImpl) ID() int {
	return s.id
}
func (s *stageImpl) IncomingSchema() sif.Schema {
	return s.incomingSchema
}