Binary tree is one of the most important data structures in the programming world. The basic definition can be given as follows (as mentioned in one of the data structures book by Tenenbaum).

A binary tree that uses cryptographic hash algorithms ... and one or more attributes are added to the leaves. In a Merkle tree structure, leaves compute their own attributes' hash, and parents ...

Because the decision tree model was trained using normalized and encoded data, the x-input must be normalized and encoded in the same way. Notice the double square brackets on the x-input. The predict ...