You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: graph.go
    path of file: ./repos/corteza/server/pkg/wfexec
    
    the code of the file until where you have to start completion: package wfexec

import (
	"context"
)

type (
	// list of Graph steps with relations
	Graph struct {
		steps    []Step
		children map[Step][]Ste
    
func (g *Graph) Orphans() (oo Steps) {
	for _, step := range g.steps {
		if len(g.Parents(step)) > 0 {
			continue
		}

		oo = append(oo, step)
	}

	return
}