code: function getId(payloadPiece, conf, path, fullPayload) {
    if (isObject(payloadPiece)) {
      if (payloadPiece.id) return payloadPiece.id;
      if (Object.keys(payloadPiece).length === 1) return Object.keys(payloadPiece)[0];
    }
  
    if (isString(payloadPiece)) return payloadPiece;
    error('wildcardFormatWrong', conf, path, payloadPiece);
    return false;
  }
docs: gets an ID from a single piece of payload.
  
  @param {object, string} payload
  @param {object} conf (optional - for error handling) the vuex-easy-access config
  @param {string} path (optional - for error handling) the path called
  @param {array|object|string} fullPayload (optional - for error handling) the full payload on which each was `getId()` called
  @returns {string} the id