code: function validate (o) {
    if (-1 === o.db.w || 0 === o.db.w) {
      if (o.db.journal || o.db.fsync || o.db.safe) {
        throw new Error(
            'Invalid writeConcern: '
          + 'w set to -1 or 0 cannot be combined with safe|fsync|journal');
      }
    }
  }
docs: /*!
  Validates the driver db options.
  
  @param {Object} o