nl_tokens: https : // dom . spec . whatwg . org / #find - flattened - slotables
pl_tokens: function findFlattenedSlotables ( slot ) { const result = [ ] ; const root = getRoot ( slot ) ; if ( ! isShadowRoot ( root ) ) { return result ; } const slotables = findSlotable ( slot ) ; if ( slotables . length === 0 ) { for ( const child of domSymbolTree . childrenIterator ( slot ) ) { if ( isSlotable ( child ) ) { slotables . push ( child ) ; } } } for ( const node of slotables ) { if ( isSlot ( node ) && isShadowRoot ( getRoot ( node ) ) ) { const temporaryResult = findFlattenedSlotables ( node ) ; result . <mask> ( ... temporaryResult ) ; } else { result . push ( node ) ; } } return result ; }