Argument name must be unique in scope of block. Argument name must be unique in scope of reference. Argument name must be unique in scope of all Blocks, Containers and other UI Components. Container for structuring elements of a page. Part of view that can generate appropriate content. Argument name must be unique in scope of action. Part of view that can generate appropriate content. Call public PHP methods of the block class. Apply visibility rules. Include another Handle's tags. Remove Element directive. Move Element directive. Argument name must be unique in scope of action. Argument updater.