class ActiveSupport::Cache::Store

def merged_options(call_options)

Merges the default options with ones specific to a method call. 
def merged_options(call_options)
  if call_options
    call_options = normalize_options(call_options)
    if options.empty?
      call_options
    else
      options.merge(call_options)
    end
  else
    options
  end
end