why not just diagram a true tree?

[Tasselmi]

  /**
   * Converts this tree into the string representation.
   *
   * Time - O(n)
   * Space - O(log n)
   */
  override def toString: String = 
    if (isEmpty) "."
    else "{" + left + value + right + "}"

hi, I learned a lot from your code. thanks.
IN the Tree data structure, the toString method is not visual friendly. why not just paint a tree use diagram.