nl_tokens: This data coul d come from a fetch OR from ldp comtaimner
pl_tokens: function ( kb , x , displayables ) { var t = kb . findTypeURIs ( <mask> ) for ( var k = 0 ; k < displayables . length ; k ++ ) { if ( $rdf . Util . mediaTypeClass ( displayables [ k ] ) . uri in t ) { return true } } return false }