Should the 'main edition' include EDR and PHI?

[rsdc2]

This is the current code for the edition_main property in epidoc.py:
` @Property
def edition_main(self) -> Edition | None:

    """
    Return the main edition (i.e. not transliteration or
    lemmatized edition).

    If the @subtype attribute is set to 'unsupplied',
    this is currently treated as though the 
    main edition is not present, and None is returned.
    """
    try:
        return self.body.edition_by_subtype(subtype=None) 
            # or \
            # self.body.edition_by_subtype(subtype='PHI') or \
            # self.body.edition_by_subtype(subtype='EDR')
    except ValueError as e:
        raise ValueError(f"Encountered the following error in {self.id}:\n"
                         f"{e.args[0]}")`