code: function isValidTypeDescriptor(obj) {
    const validKeys = ['type', 'payload', 'meta'];
  
    if (!isPlainObject(obj)) {
      return false;
    }
    for (let key in obj) {
      if (!~validKeys.indexOf(key)) {
        return false;
      }
    }
    if (!('type' in obj)) {
      return false;
    } else if (typeof obj.type !== 'string' && typeof obj.type !== 'symbol') {
      return false;
    }
  
    return true;
  }
docs: Is the given object a valid type descriptor?
  
  @function isValidTypeDescriptor
  @access private
  @param {object} obj - The object to check agains the type descriptor definition
  @returns {boolean}