isInstanceOf (type, parentType) {
    var NodeClass = this.getNodeClass(type)
    if (NodeClass) {
      return Node.isInstanceOf(NodeClass, parentType)
    }
    return false
  }
Checks if a given type is of given parent type.

    @param {String} type
    @param {String} parentType
    @returns {Boolean} true if type is and instance of parentType.