docs: function connection( user_options ) {
    var options = user_options || {}
  
    if ( typeof db !== 'object' ) {
      options.connect = user_options.connect || { useMongoClient: true }
      db = setupConnection( options )
    }
  
    try {
      return mongoose.connect( db.uri, options.connect )
    } catch ( err ) {
      throw err
    }
  }