import typing


def preservation_copy(row: typing.Mapping[str, str]) -> typing.Optional[str]:
    """A path to the original digital asset in the 'Masters/' netapp mount.

    If the File Name starts with "Masters/", it will be used as is. Otherwise,
    it will be prepended with "Masters/dlmasters/", in order to match the
    content of DLCS exports.

    Args:
        row: An input CSV record.

    Returns:
        String representing a path, or None.
    """

    file_path = row.get("File Name")
    if not file_path:
        return None
    if not str(file_path).startswith("Masters/"):
        return "Masters/" + file_path
    return file_path