hash deep_select

Hash.class_eval do
    def deep_select(key)
        res=[]
        res << self[key]
        values.select{|v| v.is_a?(Hash)}.each do |h|
            children=h.deep_select(key)
            res += children if children
        end
        res.compact!
        res.empty? ? nil : res
    end
end