def _normalize_assets(self, assets):
        """
        Perform asset normalization. For some reason, assets that are sometimes
        present in lectures, have "@1" at the end of their id. Such "uncut"
        asset id when fed to OPENCOURSE_ASSETS_URL results in error that says:
        "Routing error: 'get-all' not implemented". To avoid that, the last
        two characters from asset id are cut off and after that that method
        works fine. It looks like, Web UI is doing the same.

        @param assets: List of asset ids.
        @type assets: [str]

        @return: Normalized list of asset ids (without trailing "@1")
        @rtype: [str]
        """
        new_assets = []

        for asset in assets:
            # For example: giAxucdaEeWJTQ5WTi8YJQ@1
            if len(asset) == 24:
                # Turn it into: giAxucdaEeWJTQ5WTi8YJQ
                asset = asset[:-2]
            new_assets.append(asset)

        return new_assets