class Object

def bullet_key
  "#{self.class}:#{bullet_primary_key_value}"
end

def bullet_primary_key_value
  return if respond_to?(:persisted?) && !persisted?
  if self.class.respond_to?(:primary_keys) && self.class.primary_keys
    self.class.primary_keys.map { |primary_key| send primary_key }.join(',')
  elsif self.class.respond_to?(:primary_key) && self.class.primary_key
    send self.class.primary_key
  else
    id
  end
end