this.has = function(conn, coll, label, value, type, callback) {
        if (label === undefined || value === undefined || type == undefined)
            return callback('Some arguments are missing!');
        if (typeof label !== 'string' || typeof type !== 'string')
            return callback('ARG1 and ARG3 must be strings!');
        type = type.toLowerCase();
        if (type !== 'vertex' && type !== 'edge' &&  type !== 'all')
            return callback("ARG3 must take as value 'vertex', 'edge' or 'all'!");
        var query = gremlin();
        async.auto({
            V: function(cb) {
                if (type === 'all' || type === 'vertex') {
                    if (typeof value == 'string')
                        query("g.V.has(%s, %s)", label, value);
                    else
                        query("g.V.has(%s, %d)", label, value);
                    client.execute(query, function(err, response) {
                        return cb(err, response.results);
                    });
                } else
                    cb(null);
            },
            E: function(cb) {
                if (type === 'all' || type === 'edge') {
                    if (typeof value == 'string')
                        query("g.E.has(%s, %s)", label, value);
                    else
                        query("g.E.has(%s, %d)", label, value);
                    client.execute(query, function(err, response) {
                        return cb(err, response.results);
                    });
                } else
                    cb(null);
            },
            has: ['V', 'E', function(cb, results) {
                if (results.V && !results.E)
                    cb(null, results.V);
                if (results.E && !results.V)
                    cb(null, results.E);
                if (results.V && results.E) {
                    results.V.merge(results.E)
                    cb(null, results.V);
                }
            }]
        }, function(err, res) {
            callback(err, res.has);
        });
    }