def add_or_merge(dictionary, key, values):
    """
    Add or merge the values in 'values' to 'dictionary' at 'key'
    """
    if key in dictionary:
        if isinstance(values, list):
            dictionary[key] = dictionary[key] + values
        else:
            dictionary[key].update(values)
    else:
        dictionary[key] = values

    return dictionary