     getParticipants: (id) ->
       Promise.resolve()
       .then =>
+        validateId(id)
         @storageClient.getObjectMetadata(id)
       .then (metadata) ->
         usernames = _.chain([metadata.owners, metadata.readers, metadata.writers])

  SharingClient = require 'kryptnostic.sharing-client'

  log = Logger.get('PermissionChangeVisitor')

  #
  # Changes permissions on the visited object nodes.

    visit: (id) ->
      Promise.resolve()
      .then =>
        validateId(id)
        @changePermissions(id)
      .then =>
        @changed.push(id)
