code: @Override
      public boolean containsKey(String key)
      {
          if (overrideProperties.containsKey(key)) {
              return true;
          }
          for (Configuration config : configList)
          {
              if (config.containsKey(key))
              {
                  return true;
              }
          }
          return false;
      }
docs: Check if the any of the sub configurations contains the specified key.
  
  @param key the key whose presence in this configuration is to be tested
  
  @return <code>true</code> if the configuration contains a value for this
  key, <code>false</code> otherwise