Delete documents by given query.

async def delete_entries(cls, db, query):
        ''' Delete documents by given query. '''
        query = cls.process_query(query)
        for i in cls.connection_retries():
            try:
                result = await db[cls.get_collection_name()].delete_many(query)
                return result
            except ConnectionFailure as ex:
                exceed = await cls.check_reconnect_tries_and_wait(i, 'delete_entries')
                if exceed:
                    raise ex