in src/extensions/visualExtensions.ts [135:138]
VisualDescriptor.prototype.removeDataField = function(this: VisualDescriptor, dataRole: string, index: number): Promise<IError> {
const url = `/report/pages/${this.page.name}/visuals/${this.name}/dataroles/${dataRole}/fields/${index}`;
return VisualExtensions.delete<IError>(this, url, index);
};