docs: def MigrateInstance(r, instance, mode=None, cleanup=None):
      """
      Migrates an instance.
  
      @type instance: string
      @param instance: Instance name
      @type mode: string
      @param mode: Migration mode
      @type cleanup: bool
      @param cleanup: Whether to clean up a previously failed migration
      """
  
      body = {}
  
      if mode is not None:
          body["mode"] = mode
  
      if cleanup is not None:
          body["cleanup"] = cleanup
  
      return r.request("put", "/2/instances/%s/migrate" % instance,
                       content=body)