code: func functions(t *cc.TranslationUnit) ([]bg.Declaration, error) {
  	filter := func(d *cc.Declarator) bool {
  		if d.Type.Kind() != cc.Function {
  			return false
  		}
  		return true
  	}
  	return bg.Get(t, filter)
  }
docs: // functions say we only want functions declared