code: @Override
      public void _whereRegex(String fieldName, String pattern) {
          List<QueryToken> tokens = getCurrentWhereTokens();
          appendOperatorIfNeeded(tokens);
          negateIfNeeded(tokens, fieldName);
  
          WhereParams whereParams = new WhereParams();
          whereParams.setValue(pattern);
          whereParams.setFieldName(fieldName);
  
          String parameter = addQueryParameter(transformValue(whereParams));
  
          WhereToken whereToken = WhereToken.create(WhereOperator.REGEX, fieldName, parameter);
          tokens.add(whereToken);
      }
docs: Matches fields where Regex.IsMatch(filedName, pattern)
  @param fieldName Field name to use
  @param pattern Regexp pattern