def inherited(base)
      dup = _validators.dup
      base._validators = dup.each { |k, v| dup[k] = v.dup }
      super
    end
def inherited(base)
      dup = _validators.dup
      base._validators = dup.each { |k, v| dup[k] = v.dup }
      super
    end
Copy validators on inheritance.