add(type, target, targetMode) {
        const node = {
            name: "Relationship",
            attributes: {
                Id: `rId${this._nextId++}`,
                Type: `${RELATIONSHIP_SCHEMA_PREFIX}${type}`,
                Target: target
            }
        };

        if (targetMode) {
            node.attributes.TargetMode = targetMode;
        }

        this._node.children.push(node);
        return node;
    }
Add a new relationship.
@param {string} type - The type of relationship.
@param {string} target - The target of the relationship.
@param {string} [targetMode] - The target mode of the relationship.
@returns {{}} The new relationship.