code: public static Bson regex(final String fieldName, final String pattern) {
          return regex(fieldName, pattern, null);
      }
docs: Creates a filter that matches all documents where the value of the field matches the given regular expression pattern with the given
  options applied.
  
  @param fieldName the field name
  @param pattern   the pattern
  @return the filter
  @mongodb.driver.manual reference/operator/query/regex $regex