def flags_from_dict(kw):
    """
    This turns a dict with keys that are flags (e.g. for CLOSECIRCUIT,
    CLOSESTREAM) only if the values are true.
    """

    if len(kw) == 0:
        return ''

    flags = ''
    for (k, v) in kw.items():
        if v:
            flags += ' ' + str(k)
    # note that we want the leading space if there's at least one
    # flag.
    return flags
This turns a dict with keys that are flags (e.g. for CLOSECIRCUIT,
    CLOSESTREAM) only if the values are true.