code: @SuppressWarnings("unchecked")
    protected Set<String> getKeys(String prefix)
    {
  
      Set<String> result = new HashSet<String>();
  
      @SuppressWarnings("rawtypes")
      final Set keys = new HashSet();
      keys.addAll(session.getUserProperties().keySet());
      keys.addAll(project.getProperties().keySet());
  
      if (prefix == null) return keys;
  
      for (Object key : keys) {
        if (((String) key).startsWith(prefix))
          result.add((String) key);
      }
  
      return result;
    }
docs: Returns all keys of project properties and user properties matching the <code>prefix</code>.
  
  @param prefix
  all keys if null
  @return