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

key 

        # Hash.key

(from ruby core)
---
    hash.key(value) -> key or nil

---

Returns the key for the first-found entry with the given `value` (see
[Entry Order](#class-Hash-label-Entry+Order)):
    h = {foo: 0, bar: 2, baz: 2}
    h.key(0) # => :foo
    h.key(2) # => :bar

Returns `nil` if so such value is found.

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.