def clear(options = {})
      invoke(:clear, '*') do |store|
        if options[:async]
          store.flushdb(async: true)
        else
          store.flushdb
        end
      end
    end
def clear(options = {})
      invoke(:clear, '*') do |store|
        if options[:async]
          store.flushdb(async: true)
        else
          store.flushdb
        end
      end
    end
Clear the entire cache by flushing the current database.

 This flushes everything in the current database, with no globbing
 applied. Data in other numbered databases will be preserved.

 @option options [Hash] :async Flush the database asynchronously, only
   supported in Redis 4.0+

 @example

   cache.clear #=> 'OK'
   cache.clear(async: true) #=> 'OK'