Retrieve from the internal cache a class instance. All arguments are case-insensitive

def get(package_str, classname):
    '''Retrieve from the internal cache a class instance. All arguments are case-insensitive''' 
    if (package_str in _dynamo_cache) and (classname in _dynamo_cache[package_str]):
        return _dynamo_cache[package_str][classname]
    return None