nl_tokens: / *
pl_tokens: function shouldNotHaveDuplicateLabels ( <mask> ) { for ( var label , visited = { } , j = 0 ; j < row . length ; j += 1 ) { label = row [ j ] ; if ( visited [ label ] ) { throw new Error ( 'where-data table contains duplicate label \'' + label + '\' in [' + row . join ( ', ' ) + ']' ) ; } visited [ label ] = 1 ; } }