@staticmethod
def _format_values(values):
    """Format entries returned by Field.values.

        Multiple entries are formatted as [entry1,entry2,entryN], single
        entries are formatted as entry1, empty values return a ..

        Args:
            values: entries in Field.values

        Returns:
            list with a single str element (as required by vcfpy)
        """
    values_set = sorted(set(values))
    if len(values_set) > 1:
        return [f"[{'|'.join(values_set)}]"]
    elif len(values_set) == 1:
        return [values_set.pop()]
    else:
        return ['.']
