code: func (as *Step) BaseStream(name types.StreamName) types.StreamName {
  	if as.LogNameBase == "" {
  		return name
  	}
  	return as.LogNameBase.Concat(name)
  }
docs: // BaseStream returns the supplied name prepended with this Step's base
  // log name.
  //
  // For example, if the base name is "foo/bar", BaseStream("baz") will return
  // "foo/bar/baz".