_commit (callback) {
    if (this._aborted) {
      return setImmediate(callback, new TransactionError('Transaction has been aborted.', 'EABORT'))
    }

    if (!this._acquiredConnection) {
      return setImmediate(callback, new TransactionError('Transaction has not begun. Call begin() first.', 'ENOTBEGUN'))
    }

    if (this._activeRequest) {
      return setImmediate(callback, new TransactionError("Can't commit transaction. There is a request in progress.", 'EREQINPROG'))
    }

    setImmediate(callback)
  }
@private
@param {basicCallback} [callback]
@return {Transaction}