class ActiveSupport::Callbacks::Callback

def check_conditionals(conditionals)
  if conditionals.any? { |c| c.is_a?(String) }
    raise ArgumentError, <<-MSG.squish
      Passing string to be evaluated in :if and :unless conditional
      options is not supported. Pass a symbol for an instance method,
      or a lambda, proc or block, instead.
    MSG
  end
  conditionals
end