code: public AVQuery<T> whereMatches(String key, String regex) {
      conditions.whereMatches(key, regex);
      return this;
    }
docs: Add a regular expression constraint for finding string values that match the provided regular
  expression. This may be slow for large datasets.
  
  @param key The key that the string to match is stored in.
  @param regex The regular expression pattern to match.
  @return Returns the query, so you can chain this call.