docs: def _set_index(self, schema, name, fields, **index_options):
          """
          https://www.sqlite.org/lang_createindex.html
          """
          query_str = "CREATE {}INDEX IF NOT EXISTS '{}_{}' ON {} ({})".format(
              'UNIQUE ' if index_options.get('unique', False) else '',
              schema,
              name,
              self._normalize_table_name(schema),
              ', '.join((self._normalize_name(f) for f in fields))
          )
  
          return self._query(query_str, ignore_result=True, **index_options)