def archive_coupling_dict(coupling_dict):
    """
    Turns an enzyme coupling dict of the form:

    .. code:: python

        {'AB6PGH': <Enzyme AB6PGH at 0x7f7d1371add8>,
         'ABTA': <Enzyme ABTA at 0x7f7d1371ae48>,
         'ACALD': <Enzyme ACALD at 0x7f7d1371aeb8>}

    to:

    .. code:: python

        {'AB6PGH': 'AB6PGH',
         'ABTA': 'ABTA',
         'ACALD': 'ACALD'
    """
    return {k:v.id for k,v in coupling_dict.items()}