def stable_select(&block)
      #Annoyingly, default ordered hash select is not stable
      self.map{|k,v| block.call(k,v) ? [k,v] : nil}.compact
    end
def stable_select(&block)
      #Annoyingly, default ordered hash select is not stable
      self.map{|k,v| block.call(k,v) ? [k,v] : nil}.compact
    end
Version of enumerable#select for an OrderedHash which is order-preserving
 Output is an array of key-value pairs.