How to use the @graphql-box/helpers.addChildField function in @graphql-box/helpers

private _addFieldToNode(node: FieldNode | InlineFragmentNode, key: string): void {
    if (!hasChildFields(node, key)) {
      const mockAST = parse(`{${key}}`);
      const queryNode = getOperationDefinitions(mockAST, QUERY)[0];
      const fieldsAndTypeNames = getChildFields(queryNode, key);
      if (!fieldsAndTypeNames) return;

      const { fieldNode } = fieldsAndTypeNames[0];
      addChildField(node, fieldNode, this._schema, key);
    }
  }