def _serialize_argument(rargname, value, varprops):
    """Serialize an MRS argument into the SimpleMRS format."""
    _argument = '{rargname}: {value}{props}'
    if rargname == CONSTARG_ROLE:
        value = '"{}"'.format(value)
    props = ''
    if value in varprops:
        props = ' [ {} ]'.format(
            ' '.join(
                [var_sort(value)] +
                list(map('{0[0]}: {0[1]}'.format,
                         [(k.upper(), v) for k, v in varprops[value]]))
            )
        )
        del varprops[value]  # only print props once
    return _argument.format(
        rargname=rargname,
        value=str(value),
        props=props
    )
Serialize an MRS argument into the SimpleMRS format.