code: def highlight(self, fields=None, tags=None):
          
          args = ['HIGHLIGHT']
          fields = self._mk_field_list(fields)
          if fields:
              args += ['FIELDS', str(len(fields))] + fields
          if tags:
              args += ['TAGS'] + list(tags)
  
          self._highlight_fields = args
          return self
docs: Apply specified markup to matched term(s) within the returned field(s)
  
          - **fields** If specified then only those mentioned fields are highlighted, otherwise all fields are highlighted
          - **tags** A list of two strings to surround the match.