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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _process_identities(identities):
 """ Generate the `Identities String` from an iterable of identities. :param identities: The identities to generate the features string from. :type identities: :class:`~collections.abc.Iterable` of :class:`~.disco.xso.Identity` :return: The `Identities String` :rtype: :class:`bytes` Generate the `Identities String` from the given `identities` as specified in :xep:`390`. """

    parts = [
        _process_identity(identity)
        for identity in identities
    ]
    parts.sort()
    return b"".join(parts)+b"\x1c"