message: iModels.get is called for both iModelHub and iModelBank.
  In the case of bank, contextId is not a GUID.
diff: @@ -270,7 +270,7 @@ export class IModelHandler {
  public async get(token: AccessToken, contextId: string, query: IModelQuery = new IModelQuery()): Promise<IModelRepository[]> {
  Logger.logInfo(loggingCategory, `Querying iModels in project ${contextId}`);
  ArgumentCheck.defined("token", token);
  - ArgumentCheck.validGuid("projectId", contextId);
  + ArgumentCheck.defined("contextId", contextId); // contextId is a GUID for iModelHub and a JSON representation of an IModelBankAccessContext for iModelBank.
  const imodels = await this._handler.getInstances<IModelRepository>(IModelRepository, token, this.getRelativeUrl(contextId, query.getId()), query.getQueryOptions());
  