code: function DamerauLevenshteinDistance(source, target, options) {
      var damLevOptions = _.extend(
          { transposition_cost: 1, restricted: false },
          options || {},
          { damerau: true }
      );
      return levenshteinDistance(source, target, damLevOptions);
  }
docs: /*
  Returns the Damerau-Levenshtein distance between strings. Counts the distance
  between two strings by returning the number of edit operations required to
  convert `source` into `target`.
  
  Valid edit operations are:
  - transposition, insertion, deletion, and substitution
  
  Options:
  insertion_cost: (default: 1)
  deletion_cost: number (default: 1)
  substitution_cost: number (default: 1)
  transposition_cost: number (default: 1)
  search: boolean (default: false)
  restricted: boolean (default: false)