code: func (iter Enumerator) Tee() (Enumerator, Enumerator) {
  	left, right := make(chan interface{}), make(chan interface{})
  
  	go func() {
  		for entry := range iter {
  			left <- entry
  			right <- entry
  		}
  		close(left)
  		close(right)
  	}()
  
  	return left, right
  }
docs: // Tee creates two Enumerators which will have identical contents as one another.