docs: def fuzzy(cls, field, value, boost=None, min_similarity=None, prefix_length=None):
          '''
          http://www.elasticsearch.org/guide/reference/query-dsl/fuzzy-query.html
          A fuzzy based query that uses similarity based on Levenshtein (edit distance) algorithm.
          '''
          instance = cls(fuzzy={field: {'value': value}})
          if boost is not None:
              instance['fuzzy'][field]['boost'] = boost
          if min_similarity is not None:
              instance['fuzzy'][field]['min_similarity'] = min_similarity
          if prefix_length is not None:
              instance['fuzzy'][field]['prefix_length'] = prefix_length
          return instance