nl_tokens: Filters word combinations based on keyword density if the word count is 200 or over .
pl_tokens: function filterOnDensity ( wordCombinations , wordCount , lowerLimit , upperLimit ) { return wordCombinations . <mask> ( function ( combination ) { return ( combination . getDensity ( wordCount ) >= lowerLimit && combination . getDensity ( wordCount ) < upperLimit ) ; } ) ; }