How to use the signac.common.errors.ExportError function in signac

operations[:] = []
    if len(operations):
        logger.debug("Pushing final chunk.")
        _export_pymongo(chunk, operations, index, mirrors, num_tries, timeout)
    if update:
        if ids:
            stale = set()
            for root in ids:
                docs_ = index.find({'root': root})
                all_ = {doc['_id'] for doc in docs_}
                stale.update(all_.difference(ids[root]))
            logger.info("Removing {} stale documents.".format(len(stale)))
            for _id in set(stale):
                index.delete_one(dict(_id=_id))
        else:
            raise errors.ExportError(
                "The exported docs sequence is empty! Unable to update!")

"""Export docs via operations to index and files to mirrors."""
    import pymongo
    if mirrors is not None:
        for mirror in mirrors:
            for doc in docs:
                if 'file_id' in doc:
                    export_to_mirror(doc, mirror, num_tries, timeout)
    for i in range(num_tries):
        try:
            index.bulk_write(operations)
            break
        except pymongo.errors.AutoReconnect as error:
            logger.warning(error)
            sleep(timeout)
    else:
        raise errors.ExportError()

def export_to_mirror(doc, mirror, num_tries=3, timeout=60):
    """Export a file associated with doc to mirror.

    :param doc: A document with a file_id entry.
    :param mirror: A file-system object to export the file to.
    :param num_tries: The number of automatic retry attempts in case of
        mirror connection errors.
    :type num_tries: int
    :param timeout: The time in seconds to wait before an
        automatic retry attempt.
    :type timeout: int
    :returns: The file id after successful export.
    """
    if 'file_id' not in doc:
        raise errors.ExportError("Doc '{}' does not have a file_id entry.".format(doc))
    for i in range(num_tries):
        try:
            with fetch(doc, mode='rb') as file:
                _export_to_mirror(file, doc['file_id'], mirror)
        except mirror.FileExistsError:
            logger.debug(
                "File with id '{}' already exported, skipping.".format(doc['file_id']))
            break
        except mirror.AutoRetry as error:
            logger.warning("Error during export: '{}', retrying...".format(error))
            sleep(timeout)
        else:
            logger.debug(
                "Stored file with id '{}' in mirror '{}'.".format(doc['file_id'], mirror))
            return doc['file_id']
    else:

try:
            with fetch(doc, mode='rb') as file:
                _export_to_mirror(file, doc['file_id'], mirror)
        except mirror.FileExistsError:
            logger.debug(
                "File with id '{}' already exported, skipping.".format(doc['file_id']))
            break
        except mirror.AutoRetry as error:
            logger.warning("Error during export: '{}', retrying...".format(error))
            sleep(timeout)
        else:
            logger.debug(
                "Stored file with id '{}' in mirror '{}'.".format(doc['file_id'], mirror))
            return doc['file_id']
    else:
        raise errors.ExportError(doc)