src/vs/workbench/api/common/extHostDocumentData.ts/setWordDefinitionFor
export function setWordDefinitionFor(modeId: string, wordDefinition: RegExp | undefined): void {
	if (!wordDefinition) {
		_modeId2WordDefinition.delete(modeId);
	} else {
		_modeId2WordDefinition.set(modeId, wordDefinition);
	}
}