Generate a random node mapping.
    Args:
        candidate_mapping: candidate_mapping: candidate node match list
    Returns:
        randomly-generated node mapping between two AMRs

def random_init_mapping(candidate_mapping):
    """
    Generate a random node mapping.
    Args:
        candidate_mapping: candidate_mapping: candidate node match list
    Returns:
        randomly-generated node mapping between two AMRs

    """
    # if needed, a fixed seed could be passed here to generate same random (to help debugging)
    random.seed()
    matched_dict = {}
    result = []
    for c in candidate_mapping:
        candidates = list(c)
        if not candidates:
            # -1 indicates no possible mapping
            result.append(-1)
            continue
        found = False
        while candidates:
            # randomly generate an index in [0, length of candidates)
            rid = random.randint(0, len(candidates) - 1)
            candidate = candidates[rid]
            # check if it has already been matched
            if candidate in matched_dict:
                candidates.pop(rid)
            else:
                matched_dict[candidate] = 1
                result.append(candidate)
                found = True
                break
        if not found:
            result.append(-1)
    return result