Convert asset_convertible to an asset.

        On success, append to matches.
        On failure, append to missing.

def _lookup_generic_scalar(self,
                               obj,
                               as_of_date,
                               country_code,
                               matches,
                               missing):
        """
        Convert asset_convertible to an asset.

        On success, append to matches.
        On failure, append to missing.
        """
        result = self._lookup_generic_scalar_helper(
            obj, as_of_date, country_code,
        )
        if result is not None:
            matches.append(result)
        else:
            missing.append(obj)