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fetch 

        # Hash.fetch

(from ruby core)
---
    hash.fetch(key) -> object
    hash.fetch(key, default_value) -> object
    hash.fetch(key) {|key| ... } -> object

---

Returns the value for the given `key`, if found.
    h = {foo: 0, bar: 1, baz: 2}
    h.fetch(:bar) # => 1

If `key` is not found and no block was given, returns `default_value`:
    {}.fetch(:nosuch, :default) # => :default

If `key` is not found and a block was given, yields `key` to the block
and returns the block's return value:
    {}.fetch(:nosuch) {|key| "No key #{key}"} # => "No key nosuch"

Raises KeyError if neither `default_value` nor a block was given.

Note that this method does not use the values of either #default or
#default_proc.

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