def findunique(lst, key):
    """
    Find all unique key values for items in lst.
    For example find all ``GROUP`` values in a ``LAYER``'s ``CLASS``es

    :param list lst: A list of composite dictionaries e.g. ``layers``, ``classes``
    :param string key: The key name to search each dictionary in the list
    """
    return sorted(set([item[key.lower()] for item in lst]))