def _subset(subset, superset):
    """True if subset is a subset of superset.

    :param dict subset: subset to compare.
    :param dict superset: superset to compare.
    :return: True iif all pairs (key, value) of subset are in superset.
    :rtype: bool
    """
    result = True
    for k in subset:
        result = k in superset and subset[k] == superset[k]
        if not result:
            break
    return result
