def instances(descendants = true)
      inst = ObjectSpace.each_object(self).to_a
      descendants ? inst : inst.select { |i| i.class == self }
    end
def instances(descendants = true)
      inst = ObjectSpace.each_object(self).to_a
      descendants ? inst : inst.select { |i| i.class == self }
    end
Return all live instances of the class
 Passing false will not include instances of sub classes