This is a Ruby tree! It shows every object from the Ruby Programming Language in a tree format.

transform_keys! 

        # Hash.transform_keys!

(from ruby core)
---
    hash.transform_keys! {|key| ... } -> self
    hash.transform_keys!(hash2) -> self
    hash.transform_keys!(hash2) {|other_key| ...} -> self
    hash.transform_keys! -> new_enumerator

---

Same as Hash#transform_keys but modifies the receiver in place instead
of returning a new hash.

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.