nl_tokens: TODO : Document
pl_tokens: function ( cb ) { return new Promise ( ( resolve /*, reject*/ ) => { let transaction = this . db . transaction ( [ 'nodes' ] , 'readonly' ) ; let cursorReq = transaction . objectStore ( 'nodes' ) . openCursor ( ) ; cursorReq . onsuccess = ( evt ) => { let cursor = evt . <mask> . result ; if ( cursor ) { cb ( this . migrate ( cursor . value ) ) ; cursor . continue ( ) ; } else { resolve ( ) ; } } ; } ) ; }