'Bulk creates VisibleBlocks for the given iterator of
BlockRecordList objects and updates the VisibleBlocks cache
for the block records\' course with the new VisibleBlocks.
Returns the newly created visible blocks.'

@classmethod
def bulk_create(cls, course_key, block_record_lists):

    created = cls.objects.bulk_create([VisibleBlocks(blocks_json=brl.json_value, hashed=brl.hash_value, course_id=course_key) for brl in block_record_lists])
    cls._update_cache(course_key, created)
    return created
