`instance`

    { :clients => [ client, client, ... ], :transport => ..., :timer => ... }

Each `client` is the `Rack::SocketIO::Application` instance for a client connection.

`instance[:clients]`

    [ client, client, ... ]

`instance[:clients].map { |client| [ client.id, nil ] }`

    [ [ id, nil ], [ id, nil ], ... ]

`instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 )`

    [ id, nil, id, nil, ... ]

`Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ]

    { id => nil, id => nil, ... }


`[ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]`



`[ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]`

`[ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]`

    [ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]

    [ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]

    [ resource, Hash[ :clients => Hash[ * instance[:clients].map { |client| [ client.id, nil ] } .flatten( 1 ) ] ] ]