code: protected ConfigProperties getChild(String key, boolean create) {
  
      if ((key == null) || (key.isEmpty())) {
        return this;
      }
      if (key.indexOf(KEY_SEPARATOR) > 0) {
        String[] segments = key.split("\\.");
        return getChild(create, segments);
      }
      SimpleConfigProperties result = this.childMap.get(key);
      if (result == null) {
        result = createChild(key, create);
        if (result == null) {
          return EMPTY;
        } else {
          this.childMap.put(key, result);
          this.nodeModifications++;
        }
      }
      return result;
    }
docs: @see #getChild(String)
  
  @param key the key of the requested child.
  @param create - {@code true} to create if not exits, {@code false} otherwise.
  @return the requested child.