'Returns same as _find_course_assets plus the index to the given asset or None. Does not convert
to AssetMetadata; thus, is internal.
Arguments:
asset_key (AssetKey): what to look for
Returns:
Tuple of:
- AssetMetadata[] for all assets of the given asset_key\'s type
- the index of asset in list (None if asset does not exist)'

def _find_course_asset(self, asset_key):

    course_assets = self._find_course_assets(asset_key.course_key)
    all_assets = SortedAssetList(iterable=[])
    all_assets.extend(course_assets.setdefault(asset_key.block_type, []))
    idx = all_assets.find(asset_key)
    return (course_assets, idx)
