clearJoined(field) {

    let relationship = this.relationship(field);

    if (!relationship) {

      throw new Error(`No relationship named "${field}" exists`);

    }

    this._joinsList = this._joinsList.filter((joinName) => {
      return joinName !== field;
    });

    let value = this._joinsCache[field];

    delete this._joinsCache[field];

    return value;

  }
Clear a joined object (Model or ModelArray)
@param {string} field The field (name of the join relationship)