class Redis::Distributed

def zunionstore(destination, *keys, **options)

Add multiple sorted sets and store the resulting sorted set in a new key. 
def zunionstore(destination, *keys, **options)
  keys.flatten!(1)
  ensure_same_node(:zunionstore, [destination].concat(keys)) do |node|
    node.zunionstore(destination, keys, **options)
  end
end