def redis_key(*args):
<EOL>return '<STR_LIT::>'.join(str(a) for a in args if a is not None)<EOL>
Create a string key from a hierarchical structure.

    :param args: list of keys to denote hierarchy
    :type args: list(str)
    :return: string representation of args
    :rtype: str

    :Example:
        >>> redis_key(['project', 'module', 'class'])
        'project:module:class'